Methods and procedures for channel measurements and reporting mechanisms

ABSTRACT

A wireless transmit/receive unit (WTRU) may receive configuration information indicating a plurality of sets of resource elements (REs). Each of the plurality of sets of REs may be associated with a Channel-State-Information Reference Signal (CSI-RS) configuration. Also, the WTRU may receive a request in a Downlink Control Information (DCI) signal, in a first time unit, to receive at least one CSI-RS, in at least one set of the plurality of sets of REs, in the first time unit, to perform a measurement and to report the measurement; and the request may indicate the at least one set of the plurality of sets of REs. Further, the WTRU may receive the at least one CSI-RS, in the at least one set of the plurality of sets of REs, in the first time unit, according to the request. Moreover, the WTRU may perform the measurement of the at least one CSI-RS.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/526,667 filed May 12, 2017, which issued on Apr. 14, 2020 as U.S.Pat. No. 10,623,978, which is the U.S. National Stage, under 35 U.S.C. §371, of International Application No. PCT/US2015/060588 filed Nov. 13,2015, which claims the benefit of U.S. Provisional Application No.62/080,004 filed Nov. 14, 2014 and U.S. Provisional Application No.62/204,274 filed Aug. 12, 2015, the contents of which are herebyincorporated by reference herein.

BACKGROUND

Unlicensed spectrum which may have traditionally been used fornon-cellular services and applications such as Wi-Fi, may be consideredby cellular operators as a complementary tool to augment their serviceofferings to meet the increasingly high demand for broadband data.

SUMMARY

A method and apparatus for channel measurements and reporting mechanismsfor Long Term Evolution (LTE) operation in an unlicensed band in awireless transmit/receive unit (WTRU) are disclosed herein. The methodincludes that the WTRU may be in communication with a primary celloperating in a licensed band and a secondary cell operating in anunlicensed band. The WTRU may receive a request in a Downlink ControlInformation (DCI) signal for measurement and reporting, wherein therequest may indicate at least one time/frequency resource in at leastone subframe for performing a measurement in an unlicensed band. TheWTRU may then perform the measurement according to the request. and senda measurement report based on the performed measurement.

In an example, the indicated at least one time/frequency resource may bea set of physical resource blocks (PRBs) or resource elements (REs). Inanother example, the indicated at least one time/frequency resource maycorrespond to a set of REs which may include REs used for one or more ofa Channel-State-Information Reference Signal (CSI-RS), aCSI-Interference Measurement (IM), a zero-power CSI-RS or aCell-specific Reference Signal (CRS).

In a further example, the at least one subframe for performing themeasurement may be the subframe of the request or a window of subframesbeginning with the subframe of the request. In yet another example, themeasurement report may include an identification of a subframe or SystemFrame Number (SFN) associated with the measurement.

In still another example, the method includes receiving an indicationfrom an evolved Node B (eNode-B), wherein the indication indicates timeand frequency resources for performing measurements, performingmeasurements on the indicated time and frequency resources, andreporting the measurements to the eNode-B.

In an additional example, a WTRU may receive, from a base station,configuration information indicating a plurality of sets of resourceelements (REs). Each of the plurality of sets of REs may be associatedwith a Channel-State-Information Reference Signal (CSI-RS)configuration. Also, the WTRU may receive a request in a DownlinkControl Information (DCI) signal, in a first time unit, to receive atleast one CSI-RS, in at least one set of the plurality of sets of REs,in the first time unit, to perform a measurement and to report themeasurement. Additionally, the request may indicate the at least one setof the plurality of sets of REs.

Further, the WTRU may receive the at least one CSI-RS, in the at leastone set of the plurality of sets of REs, in the first time unit,according to the request. Moreover, the WTRU may perform the measurementof the at least one CSI-RS. Accordingly, the WTRU may transmit, to thebase station, in at least one of the first time unit and a second timeunit, a measurement report based on the performed measurement.

In another example, the measurement report may include an identificationof the first time unit used to receive the at least one CSI-RS. Also,the measurement report may include an identification of a System FrameNumber (SFN).

In a further example, the first time unit may be a first subframe andthe second time unit may be a second subframe. Moreover, the firstsubframe may include a first plurality of slots and the second subframemay include a second plurality of slots. Also, the first time unit maybe a first slot and the second time unit may be a second slot.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding may be had from the following description,given by way of example in conjunction with the accompanying drawingswherein:

FIG. 1A is a system diagram of an example communications system in whichone or more disclosed embodiments may be implemented;

FIG. 1B is a system diagram of an example wireless transmit/receive unit(WTRU) that may be used within the communications system illustrated inFIG. 1A;

FIG. 1C is a system diagram of an example radio access network and anexample core network that may be used within the communications systemillustrated in FIG. 1A;

FIG. 2 is a system diagram of an example Licensed-Assisted Access (LAA)scenario;

FIG. 3 is a system diagram of an example LAA system usingListen-Before-Talk (LBT);

FIG. 4 is a signaling diagram of an example method for channelmeasurement and reporting mechanisms for Long Term Evolution (LTE)operation in an unlicensed band;

FIG. 5 is a system diagram of an example of a wireless system includinga hidden node; and

FIG. 6 is a signaling diagram of another example method for channelmeasurements and reporting mechanisms for LTE operation in an unlicensedband.

DETAILED DESCRIPTION

FIG. 1A is a diagram of an example communications system 100 in whichone or more disclosed embodiments may be implemented. The communicationssystem 100 may be a multiple access system that provides content, suchas voice, data, video, messaging, broadcast, and the like, to multiplewireless users. The communications system 100 may enable multiplewireless users to access such content through the sharing of systemresources, including wireless bandwidth. For example, the communicationssystems 100 may employ one or more channel access methods, such as codedivision multiple access (CDMA), time division multiple access (TDMA),frequency division multiple access (FDMA), orthogonal FDMA (OFDMA),single-carrier FDMA (SC-FDMA), and the like.

As shown in FIG. 1A, the communications system 100 may include wirelesstransmit/receive units (WTRUs) 102 a, 102 b, 102 c, 102 d, a radioaccess network (RAN) 104, a core network 106, a public switchedtelephone network (PSTN) 108, the Internet 110, and other networks 112,though it will be appreciated that the disclosed embodiments contemplateany number of WTRUs, base stations, networks, and/or network elements.Each of the WTRUs 102 a, 102 b, 102 c, 102 d may be any type of deviceconfigured to operate and/or communicate in a wireless environment. Byway of example, the WTRUs 102 a, 102 b, 102 c, 102 d may be configuredto transmit and/or receive wireless signals and may include userequipment (UE), a mobile station, a fixed or mobile subscriber unit, apager, a cellular telephone, a personal digital assistant (PDA), asmartphone, a laptop, a netbook, a personal computer, a wireless sensor,consumer electronics, and the like.

The communications systems 100 may also include a base station 114 a anda base station 114 b. Each of the base stations 114 a, 114 b may be anytype of device configured to wirelessly interface with at least one ofthe WTRUs 102 a, 102 b, 102 c, 102 d to facilitate access to one or morecommunication networks, such as the core network 106, the Internet 110,and/or the other networks 112. By way of example, the base stations 114a, 114 b may be a base transceiver station (BTS), a Node-B, an eNode B,a Home Node B, a Home eNode B, a site controller, an access point (AP),a wireless router, and the like. While the base stations 114 a, 114 bare each depicted as a single element, it will be appreciated that thebase stations 114 a, 114 b may include any number of interconnected basestations and/or network elements.

The base station 114 a may be part of the RAN 104, which may alsoinclude other base stations and/or network elements (not shown), such asa base station controller (BSC), a radio network controller (RNC), relaynodes, and the like The base station 114 a and/or the base station 114 bmay be configured to transmit and/or receive wireless signals within aparticular geographic region, which may be referred to as a cell (notshown). The cell may further be divided into cell sectors. For example,the cell associated with the base station 114 a may be divided intothree sectors. Thus, in one embodiment, the base station 114 a mayinclude three transceivers, i.e., one for each sector of the cell. Inanother embodiment, the base station 114 a may employ multiple-inputmultiple-output (MIMO) technology and, therefore, may utilize multipletransceivers for each sector of the cell.

The base stations 114 a, 114 b may communicate with one or more of theWTRUs 102 a, 102 b, 102 c, 102 d over an air interface 116, which may beany suitable wireless communication link (for example, radio frequency(RF), microwave, infrared (IR), ultraviolet (UV), visible light, and thelike). The air interface 116 may be established using any suitable radioaccess technology (RAT).

More specifically, as noted above, the communications system 100 may bea multiple access system and may employ one or more channel accessschemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. Forexample, the base station 114 a in the RAN 104 and the WTRUs 102 a, 102b, 102 c may implement a radio technology such as Universal MobileTelecommunications System (UMTS) Terrestrial Radio Access (UTRA), whichmay establish the air interface 116 using wideband CDMA (WCDMA). WCDMAmay include communication protocols such as High-Speed Packet Access(HSPA) and/or Evolved HSPA (HSPA+). HSPA may include High-Speed DownlinkPacket Access (HSDPA) and/or High-Speed Uplink Packet Access (HSUPA).

In another embodiment, the base station 114 a and the WTRUs 102 a, 102b, 102 c may implement a radio technology such as Evolved UMTSTerrestrial Radio Access (E-UTRA), which may establish the air interface116 using Long Term Evolution (LTE) and/or LTE-Advanced (LTE-A).

In other embodiments, the base station 114 a and the WTRUs 102 a, 102 b,102 c may implement radio technologies such as IEEE 802.16 (i.e.,Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000,CDMA2000 1×, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), InterimStandard 95 (IS-95), Interim Standard 856 (IS-856), Global System forMobile communications (GSM), Enhanced Data rates for GSM Evolution(EDGE), GSM EDGE (GERAN), and the like.

The base station 114 b in FIG. 1A may be a wireless router, Home Node B,Home eNode B, or access point, for example, and may utilize any suitableRAT for facilitating wireless connectivity in a localized area, such asa place of business, a home, a vehicle, a campus, and the like. In oneembodiment, the base station 114 b and the WTRUs 102 c, 102 d mayimplement a radio technology such as IEEE 802.11 to establish a wirelesslocal area network (WLAN). In another embodiment, the base station 114 band the WTRUs 102 c, 102 d may implement a radio technology such as IEEE802.15 to establish a wireless personal area network (WPAN). In yetanother embodiment, the base station 114 b and the WTRUs 102 c, 102 dmay utilize a cellular-based RAT (for example, WCDMA, CDMA2000, GSM,LTE, LTE-A, and the like) to establish a picocell or femtocell. As shownin FIG. 1A, the base station 114 b may have a direct connection to theInternet 110. Thus, the base station 114 b may not be required to accessthe Internet 110 via the core network 106.

The RAN 104 may be in communication with the core network 106, which maybe any type of network configured to provide voice, data, applications,and/or voice over internet protocol (VoIP) services to one or more ofthe WTRUs 102 a, 102 b, 102 c, 102 d. For example, the core network 106may provide call control, billing services, mobile location-basedservices, pre-paid calling, Internet connectivity, video distribution,and the like, and/or perform high-level security functions, such as userauthentication. Although not shown in FIG. 1A, it will be appreciatedthat the RAN 104 and/or the core network 106 may be in direct orindirect communication with other RANs that employ the same RAT as theRAN 104 or a different RAT. For example, in addition to being connectedto the RAN 104, which may be utilizing an E-UTRA radio technology, thecore network 106 may also be in communication with another RAN (notshown) employing a GSM radio technology.

The core network 106 may also serve as a gateway for the WTRUs 102 a,102 b, 102 c, 102 d to access the PSTN 108, the Internet 110, and/orother networks 112. The PSTN 108 may include circuit-switched telephonenetworks that provide plain old telephone service (POTS). The Internet110 may include a global system of interconnected computer networks anddevices that use common communication protocols, such as thetransmission control protocol (TCP), user datagram protocol (UDP) andthe internet protocol (IP) in the TCP/IP internet protocol suite. Thenetworks 112 may include wired or wireless communications networks ownedand/or operated by other service providers. For example, the networks112 may include another core network connected to one or more RANs,which may employ the same RAT as the RAN 104 or a different RAT.

Some or all of the WTRUs 102 a, 102 b, 102 c, 102 d in thecommunications system 100 may include multi-mode capabilities, i.e., theWTRUs 102 a, 102 b, 102 c, 102 d may include multiple transceivers forcommunicating with different wireless networks over different wirelesslinks. For example, the WTRU 102 c shown in FIG. 1A may be configured tocommunicate with the base station 114 a, which may employ acellular-based radio technology, and with the base station 114 b, whichmay employ an IEEE 802 radio technology.

FIG. 1B is a system diagram of an example WTRU 102. As shown in FIG. 1B,the WTRU 102 may include a processor 118, a transceiver 120, atransmit/receive element 122, a speaker/microphone 124, a keypad 126, adisplay/touchpad 128, non-removable memory 130, removable memory 132, apower source 134, a global positioning system (GPS) chipset 136, andother peripherals 138. It will be appreciated that the WTRU 102 mayinclude any sub-combination of the foregoing elements while remainingconsistent with an embodiment.

The processor 118 may be a general purpose processor, a special purposeprocessor, a conventional processor, a digital signal processor (DSP), aplurality of microprocessors, one or more microprocessors in associationwith a DSP core, a controller, a microcontroller, Application SpecificIntegrated Circuits (ASICs), Field Programmable Gate Array (FPGAs)circuits, any other type of integrated circuit (IC), a state machine,and the like. The processor 118 may perform signal coding, dataprocessing, power control, input/output processing, and/or any otherfunctionality that enables the WTRU 102 to operate in a wirelessenvironment. The processor 118 may be coupled to the transceiver 120,which may be coupled to the transmit/receive element 122. While FIG. 1Bdepicts the processor 118 and the transceiver 120 as separatecomponents, it will be appreciated that the processor 118 and thetransceiver 120 may be integrated together in an electronic package orchip.

The transmit/receive element 122 may be configured to transmit signalsto, or receive signals from, a base station (for example, the basestation 114 a) over the air interface 116. For example, in oneembodiment, the transmit/receive element 122 may be an antennaconfigured to transmit and/or receive RF signals. In another embodiment,the transmit/receive element 122 may be an emitter/detector configuredto transmit and/or receive IR, UV, or visible light signals, forexample. In yet another embodiment, the transmit/receive element 122 maybe configured to transmit and receive both RF and light signals. It willbe appreciated that the transmit/receive element 122 may be configuredto transmit and/or receive any combination of wireless signals.

In addition, although the transmit/receive element 122 is depicted inFIG. 1B as a single element, the WTRU 102 may include any number oftransmit/receive elements 122. More specifically, the WTRU 102 mayemploy MIMO technology. Thus, in one embodiment, the WTRU 102 mayinclude two or more transmit/receive elements 122 (for example, multipleantennas) for transmitting and receiving wireless signals over the airinterface 116.

The transceiver 120 may be configured to modulate the signals that areto be transmitted by the transmit/receive element 122 and to demodulatethe signals that are received by the transmit/receive element 122. Asnoted above, the WTRU 102 may have multi-mode capabilities. Thus, thetransceiver 120 may include multiple transceivers for enabling the WTRU102 to communicate via multiple RATs, such as UTRA and IEEE 802.11, forexample.

The processor 118 of the WTRU 102 may be coupled to, and may receiveuser input data from, the speaker/microphone 124, the keypad 126, and/orthe display/touchpad 128 (for example, a liquid crystal display (LCD)display unit or organic light-emitting diode (OLED) display unit). Theprocessor 118 may also output user data to the speaker/microphone 124,the keypad 126, and/or the display/touchpad 128. In addition, theprocessor 118 may access information from, and store data in, any typeof suitable memory, such as the non-removable memory 130 and/or theremovable memory 132. The non-removable memory 130 may includerandom-access memory (RAM), read-only memory (ROM), a hard disk, or anyother type of memory storage device. The removable memory 132 mayinclude a subscriber identity module (SIM) card, a memory stick, asecure digital (SD) memory card, and the like. In other embodiments, theprocessor 118 may access information from, and store data in, memorythat is not physically located on the WTRU 102, such as on a server or ahome computer (not shown).

The processor 118 may receive power from the power source 134, and maybe configured to distribute and/or control the power to the othercomponents in the WTRU 102. The power source 134 may be any suitabledevice for powering the WTRU 102. For example, the power source 134 mayinclude one or more dry cell batteries (for example, nickel-cadmium(NiCd), nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion(Li-ion), and the like), solar cells, fuel cells, and the like.

The processor 118 may also be coupled to the GPS chipset 136, which maybe configured to provide location information (for example, longitudeand latitude) regarding the current location of the WTRU 102. Inaddition to, or in lieu of, the information from the GPS chipset 136,the WTRU 102 may receive location information over the air interface 116from a base station (for example, base stations 114 a, 114 b) and/ordetermine its location based on the timing of the signals being receivedfrom two or more nearby base stations. It will be appreciated that theWTRU 102 may acquire location information by way of any suitablelocation-determination method while remaining consistent with anembodiment.

The processor 118 may further be coupled to other peripherals 138, whichmay include one or more software and/or hardware modules that provideadditional features, functionality and/or wired or wirelessconnectivity. For example, the peripherals 138 may include anaccelerometer, an e-compass, a satellite transceiver, a digital camera(for photographs or video), a universal serial bus (USB) port, avibration device, a television transceiver, a hands free headset, aBluetooth® module, a frequency modulated (FM) radio unit, a digitalmusic player, a media player, a video game player module, an Internetbrowser, and the like.

FIG. 1C is a system diagram of the RAN 104 and the core network 106according to an embodiment. As noted above, the RAN 104 may employ anE-UTRA radio technology to communicate with the WTRUs 102 a, 102 b, 102c over the air interface 116. The RAN 104 may also be in communicationwith the core network 106.

The RAN 104 may include eNode-Bs 140 a, 140 b, 140 c, though it will beappreciated that the RAN 104 may include any number of eNode-Bs whileremaining consistent with an embodiment. The eNode-Bs 140 a, 140 b, 140c may each include one or more transceivers for communicating with theWTRUs 102 a, 102 b, 102 c over the air interface 116. In one embodiment,the eNode-Bs 140 a, 140 b, 140 c may implement MIMO technology. Thus,the eNode-B 140 a, for example, may use multiple antennas to transmitwireless signals to, and receive wireless signals from, the WTRU 102 a.

Each of the eNode-Bs 140 a, 140 b, 140 c may be associated with aparticular cell (not shown) and may be configured to handle radioresource management decisions, handover decisions, scheduling of usersin the uplink and/or downlink, and the like. As shown in FIG. 1C, theeNode-Bs 140 a, 140 b, 140 c may communicate with one another over an X2interface.

The core network 106 shown in FIG. 1C may include a mobility managemententity gateway (MME) 142, a serving gateway 144, and a packet datanetwork (PDN) gateway 146. While each of the foregoing elements aredepicted as part of the core network 106, it will be appreciated thatany one of these elements may be owned and/or operated by an entityother than the core network operator.

The MME 142 may be connected to each of the eNode-Bs 140 a, 140 b, 140 cin the RAN 104 via an S1 interface and may serve as a control node. Forexample, the MME 142 may be responsible for authenticating users of theWTRUs 102 a, 102 b, 102 c, bearer activation/deactivation, selecting aparticular serving gateway during an initial attach of the WTRUs 102 a,102 b, 102 c, and the like. The MME 142 may also provide a control planefunction for switching between the RAN 104 and other RANs (not shown)that employ other radio technologies, such as GSM or WCDMA.

The serving gateway 144 may be connected to each of the eNode Bs 140 a,140 b, 140 c in the RAN 104 via the S1 interface. The serving gateway144 may generally route and forward user data packets to/from the WTRUs102 a, 102 b, 102 c. The serving gateway 144 may also perform otherfunctions, such as anchoring user planes during inter-eNode B handovers,triggering paging when downlink data is available for the WTRUs 102 a,102 b, 102 c, managing and storing contexts of the WTRUs 102 a, 102 b,102 c, and the like.

The serving gateway 144 may also be connected to the PDN gateway 146,which may provide the WTRUs 102 a, 102 b, 102 c with access topacket-switched networks, such as the Internet 110, to facilitatecommunications between the WTRUs 102 a, 102 b, 102 c and IP-enableddevices.

The core network 106 may facilitate communications with other networks.For example, the core network 106 may provide the WTRUs 102 a, 102 b,102 c with access to circuit-switched networks, such as the PSTN 108, tofacilitate communications between the WTRUs 102 a, 102 b, 102 c andtraditional land-line communications devices. For example, the corenetwork 106 may include, or may communicate with, an IP gateway (forexample, an IP multimedia subsystem (IMS) server) that serves as aninterface between the core network 106 and the PSTN 108. In addition,the core network 106 may provide the WTRUs 102 a, 102 b, 102 c withaccess to the networks 112, which may include other wired or wirelessnetworks that are owned and/or operated by other service providers.

Wireless communication systems compliant with Third GenerationPartnership Project (3GPP) Long Term Evolution (LTE) may support up to100 megabits per second (Mbps) in the downlink (DL), and up to 50 Mbpsin the uplink (UL) for a 2×2 configuration. The LTE DL scheme may bebased on an Orthogonal Frequency Division Multiple Access (OFDMA) airinterface. Each radio frame may consist of ten subframes of 1millisecond (ms) each. Each subframe may consist of two timeslots of 0.5ms each. There may be either seven or six Orthogonal Frequency DivisionMultiplexing (OFDM) symbols per timeslot. Seven symbols per timeslot maybe used with normal cyclic prefix (CP) length, and six symbols pertimeslot may be used with extended CP length. The subcarrier spacing fora particular specification may be 15 kilohertz (kHz). A reducedsubcarrier spacing mode using 7.5 kHz may also be possible. Frame andradio frame may be used interchangeably.

A resource element (RE) may correspond to one subcarrier during one OFDMsymbol interval. Twelve consecutive subcarriers during a 0.5 ms timeslotmay constitute one resource block (RB). With seven symbols per timeslot,each RB may consist of 12×7=84 REs.

The basic time-domain unit for dynamic scheduling may be one subframeconsisting of two consecutive timeslots. This may sometimes be referredto as a RB pair. Certain subcarriers on some OFDM symbols may beallocated to carry pilot or reference signals in the time-frequencygrid. A number of subcarriers at the edges of the transmission bandwidthmay not be transmitted in order to comply with spectral maskrequirements.

Uplink channels which may be provided, and/or used, include Physical ULShared Channel (PUSCH) and/or Physical UL Control Channel (PUCCH).Control information, which may be referred to as UL Control Information(UCI), may be transmitted by a wireless transmit/receive unit (WTRU),for example in a subframe, on the PUSCH or the PUCCH, or part may betransmitted on the PUCCH and part on the PUSCH. UCI may include one ormore of hybrid automatic repeat request (HARQ) acknowledgement(ACK)/negative acknowledgement (NACK), scheduling request (SR), and/orChannel State Information (CSI) which may include one or more of ChannelQuality Indicator (CQI), Precoding Matrix Indicator (PMI), and RankIndicator (RI). Resources which may be allocated for PUCCH transmissionmay be located at or near the edges of the UL band.

Downlink channels which may be provided, and/or used, include PhysicalDownlink Shared Channel (PDSCH) and/or downlink control channels whichmay include one or more of Physical Control Format Indicator Channel(PCFICH), Physical Hybrid-ARQ Indicator Channel (PHICH), PhysicalDownlink Control Channel (PDCCH), and/or Enhanced PDCCH (EPDCCH).

The first 1 to 3 OFDM symbol(s) in each subframe in the DL may beoccupied by one or more of PCFICH, PHICH, and PDCCH according to theoverhead of the control channels, and the symbols occupied may bereferred to as the DL control region. The PCFICH may be transmitted inthe 1^(st) OFDM symbol (for example, symbol 0) in each subframe and/ormay indicate the number of OFDM symbols used for the DL control regionin the subframe. A WTRU may detect a Control Format Indicator (CFI) froma PCFICH and the DL control region may be defined in the subframeaccording to the CFI value. The PCFICH may be skipped if a subframe maybe defined as a non-PDSCH supportable subframe. DL symbols which are notpart of a DL control region may be referred to as the data or PDSCHregion. EPDCCH may be provided and/or used in the PDSCH region. Thelocation of an EPDCCH in that region may be signaled, for example viahigher layer signaling such as Radio Resource Control (RRC) signaling,to a WTRU that may (or may be expected to) monitor, receive or otherwiseuse that EPDCCH. The PDCCH and/or EPDCCH may provide controlinformation, resource allocations (for example, grants) for UL and/or DLtransmission, and the like.

DL signals and/or channels may be provided or transmitted by an eNode-Band/or may be received and/or used by a WTRU. UL signals and/or channelsmay be provided or transmitted by a WTRU and/or may be received and/orused by an eNode-B.

Signals and/or channels may be associated with a cell which maycorrespond to a certain carrier frequency and/or geographic area. Acarrier frequency may be a center frequency of a cell (for example, thecenter frequency of a cell's supported bandwidth). An eNode-B may haveone or more cells associated with it. eNode-B and cell may in someembodiments be used interchangeably.

Synchronization signals which may include a Primary SynchronizationSignal (PSS) and/or a Secondary Synchronization Signal (SSS), may beprovided or transmitted, for example by an eNode-B or cell. Such signalsmay be used by a WTRU to acquire time and/or frequency synchronizationwith an eNode-B or cell. The PSS and/or SSS may be present in subframes0 and/or 5 and may be present in every radio frame. Transmission may beon 62 subcarriers at the center of a cell's bandwidth and 5 subcarrierson each side of the 62 may be reserved or unused. For frequency divisionduplex (FDD), PSS transmission may be in the last OFDM symbol and SSS inthe 2^(nd) last (for example, next to last) OFDM symbol of timeslot 0(for example, first timeslot of subframe 0) and timeslot 10 (forexample, first timeslot of subframe 5) of each radio frame. For timedivision duplex (TDD), PSS transmission may be in the 3^(rd) OFDM symbolin subframes 1 and 6 and SSS may be transmitted in the last OFDM symbolin timeslot 1 (for example, the second timeslot of subframe 0) andtimeslot 11 (for example, the second timeslot of subframe 5) of eachradio frame. The synchronization signals may convey informationregarding the physical cell identity (cell ID) of the cell.

A Physical Broadcast Channel (PBCH) which may be transmitted by aneNode-B, may carry important cell information such as a MasterInformation Block (MIB). The PBCH may be provided or transmitted insubframe 0 of each radio frame and may be repeated in each of fourconsecutive radio frames (for example, 40 ms time period). The PBCH maybe transmitted in the first four OFDM symbols of the second timeslot ofsubframe 0 and may be transmitted on the 72 center subcarriers. The MIBmay provide information such as the DL bandwidth of the cell, PHICHinformation, and at least part of the System Frame Number (SFN), forexample the most significant 8 bits of a 10-bit SFN.

Downlink reference signals may include a Cell-specific Reference Signal(CRS) and/or a Channel-State-Information Reference Signal (CSI-RS),and/or a DeModulation Reference Signal (DM-RS), and/or a PositioningReference Signal (PRS). DL reference signals may be received and/or usedby a WTRU. CRS may be used by a WTRU for channel estimation for coherentdemodulation of a (for example, any) downlink physical channel exceptcertain DL channels which may include at least one of PMCH, EPDCCH, andPDSCH when configured with TM7, TM8, TM9, or TM10. The CRS may be usedby a WTRU for channel state information measurements for the reportingof CQI, PMI, and/or RI, for example if the WTRU is configured with atransmission mode using CRS for PDSCH demodulation. The CRS may be usedby a WTRU for cell-selection and/or mobility-related measurements. TheCRS may be received in certain subframes such as any subframe and up to4 antenna ports may be supported. DM-RS may be used by a WTRU fordemodulation of certain channels which may include at least one ofEPDCCH and PDSCH configured with TM7, TM8, TM9, or TM10. DM-RS which maybe used for the demodulation of a certain channel (for example, EPDCCHor PDSCH) may be transmitted in the resource blocks assigned to thechannel (for example, EPDCCH or PDSCH). CSI-RS, which may be transmittedwith a duty cycle, may be used by a WTRU for channel state informationmeasurements, for example if the WTRU may be configured with atransmission mode which may use DM-RS for PDSCH demodulation with theexception of certain transmission modes such as TM7 and/or TM8. TheCSI-RS may also be used for cell-selection and mobility-relatedmeasurements, for example if a WTRU may be configured with a certaintransmission mode (for example, TM10). The PRS may be used by a WTRU forposition related measurements.

For LTE TDD, multiple TDD uplink and downlink subframe configurationsmay be supported and one of the configurations may be used in aneNode-B. Each TDD uplink and downlink subframe configuration may containdownlink subframe ‘D’, uplink subframe V′, and special subframe ‘S’ asshown in Table 1.

Table 1 is an example of TDD LTE Uplink-downlink configurations.

TABLE 1 Uplink- Downlink-to- downlink Uplink configur- Switch-pointSubframe number ation periodicity 0 1 2 3 4 5 6 7 8 9 0 5 ms D S U U U DS U U U 1 5 ms D S U U D D S U U D 2 5 ms D S U D D D S U D D 3 10 ms  DS U U U D D D D D 4 10 ms  D S U U D D D D D D 5 10 ms  D S U D D D D DD D 6 5 ms D S U U U D S U U D

Conventional cellular systems, such as LTE systems, may use licensedspectrum. Operators may acquire, such as by auction from the government,the right to utilize a certain part of a frequency band in a certainarea for transmission and reception of cellular signals. By usinglicensed spectrum, an operator may have exclusive use of that spectrumto provide services to its users, for example, without concern forin-band interference from the systems of other operators.

Unlicensed spectrum which may have traditionally been used fornon-cellular services and applications such as Wi-Fi, may be consideredby cellular operators as a complementary tool to augment their serviceofferings to meet the increasingly high demand for broadband data. Oneof the deployment scenarios to consider may employ carrier aggregation.In this scenario, which may be referred to as Licensed-Assisted Access(LAA), a (or the) primary component carrier (or serving cell) (PCell)may be a licensed carrier (for example, a carrier which may use licensedspectrum). An unlicensed carrier (for example, a carrier which may useunlicensed spectrum) may be a secondary component carrier (or servingcell) (SCell) which may be aggregated with the PCell.

FIG. 2 is a system diagram of an example LAA scenario. In an example,there may be one or more unlicensed SCells and zero, one or morelicensed SCells which may be aggregated together and/or with the PCell.The PCell may be a licensed LTE PCell. In an example shown in scenario200, WTRU 202 a may use SCells or secondary carriers 211, 212, 213, andPCell or primary carrier 220. WTRU 202 b may use SCells or secondarycarriers 215, 216, 217, and PCell or primary carrier 230. With carrieraggregation, the PCell and SCells may belong to the same eNode-B. Inanother deployment scenario, dual connectivity may be employed where oneor more unlicensed carriers may belong to a different eNode-B than thelicensed PCell.

When considering LTE operation in unlicensed spectrum, coexistence ofLTE with other unlicensed technologies such as Wi-Fi, as well as amongLTE operators, may be considered in order to, for example, attempt tominimize interference and provide for fairness among the users of thespectrum. Mechanisms such as Listen-Before-Talk (LBT) and transmissiongaps may be used. With LBT, a system node such as an Access Point (AP),eNodeB (eNode-B), wireless transmit/receive unit (WTRU), and the like,may listen to a channel (for example, a frequency band with a certaincenter frequency and bandwidth) to determine if there may be anotheruser using the channel before transmitting on the channel or a portionof the channel.

FIG. 3 is a system diagram of an example LAA system using LBT. In anexample, listening and/or determination of usage by another may includeor be based on measurements which may include energy detection. Withtransmission gaps, a system node which may transmit on a channel or partof a channel may include or ensure there are gaps in its transmission,for example, to allow other potential users to see the channel as freeand/or use the channel. In an example, the other potential users may notuse the channel if they detect energy above a threshold. In an exampleshown in system 300, the LAA cell user may be silent while another useruses the channel 320. The LAA cell user may then detect a free period330. The LAA cell user may then use the channel 340. Further, hiddennodes may cause interference which an LAA cell may not detect.

LTE operation in an unlicensed spectrum, which may or may not becombined with operation in a licensed spectrum (for example, which maybe with or without aggregation or dual connectivity with a licensedPCell), may be referred to as LTE-Unlicensed operation or LTE-U. Theterms Wi-Fi, WiFi, and Wifi may be used interchangeably herein.

Use of coexistence mechanisms such as LBT and transmission gaps mayresult in transmission and/or reception issues and/or new scenarios forLTE-U which may need to be addressed. These issues and/or scenarios maybe due to the existence of gaps themselves. For example, the existingmeasurement and reporting mechanisms in LTE which may use or be based onsignals which may be regularly available, may not be applicable and/oroptimized for LTE-U operation which may involve gaps in the transmissionof some signals.

In some embodiments described herein, the terms eNode-B and cell may beused interchangeably. In some embodiments, the terms unlicensed andlicense-exempt (LE) may be used interchangeably. In some embodimentsoperate may be used interchangeably with transmit and/or receive. Insome embodiments the terms component carrier may be used interchangeablywith serving cell.

An LTE-U eNode-B may be an eNode-B or cell which may transmit and/orreceive one or more LTE channels (for example, physical channels) and/orsignals and/or may operate, for example, transmit and/or receivesignals, in a license-exempt (LE) band. The LTE-U eNode-B may transmitand/or receive one or more LTE channels and/or signals in a licensedband and/or in a LE band. In the LE band in which an LTE-U eNode-B mayoperate, one or more other radio access technologies (RATs) such asWi-Fi, one or more other LTE-U eNode-Bs, and/or one or more WTRUs mayexist and/or operate. In some embodiments, the terms eNode-B and LTE-UeNode-B, may be used interchangeably. In some embodiments WTRU may besubstituted for eNode-B and/or vice versa and still be consistent withthis disclosure. In some embodiments UL may be substituted for DL and/orvice versa and still be consistent with this disclosure. The terms LTE-Uand LAA may be used in place of each other and still be consistent withthis disclosure.

In some embodiments, a channel may refer to a frequency band which mayhave a center or carrier frequency and a bandwidth. Licensed and/orunlicensed spectrum may include one or more channels which may or maynot overlap. The terms channel, frequency channel, wireless channel, andLE channel may be used interchangeably. Accessing a channel may be thesame as using (for example, transmitting and/or receiving on or using)the channel.

In some embodiments, a channel may refer to an LTE channel or signalsuch as an uplink or downlink physical channel or signal. Downlinkchannels and signals may include one or more of PSS, SSS, PBCH, PDCCH,EPDCCH, and PDSCH. Uplink channels and signals may include one or moreof PRACH, PUCCH, SRS, and PUSCH. Channel and LTE channel may be usedinterchangeably. Channels and signals may be used interchangeably.

In some embodiments data/control may mean data and/or control signalsand/or channels. Control may include synchronization. The data/controlmay be LTE data/control. The terms data/control and data/controlchannels and/or signals may be used interchangeably. Channels andsignals may be used interchangeably. LTE and LTE-A may be usedinterchangeably.

In some embodiments channel resources may be resources (for example,3GPP LTE or LTE-A resources) such as time and/or frequency resourceswhich may, for example, at least sometimes, carry one or more channelsand/or signals. In some embodiments, channel resources may be usedinterchangeably with channels and/or signals.

Reference signal, CSI-RS, CRS, DM-RS, DRS, measurement reference signal,reference resource for measurement, CSI-Interference Measurement (IM),and measurement RS may be used interchangeably. SCell, secondary cell,LTE-U cell, license-assisted cell, unlicensed cell, and LAA cell may beused interchangeably. PCell, primary cell, LTE cell, and licensed cellmay be used interchangeably. Interference and interference plus noisemay be used interchangeably.

Methods and apparatuses using LTE-U, LTE unlicensed band, LAA, a busysignal and/or a synchronization signal are disclosed herein. Methods andapparatuses are disclosed herein for measurement handling for LTE cellsin an unlicensed band when the signals and resources to be measured maynot be regularly available. A dynamic indication (e.g., including startand duration) of signal and resource presence may indicate availabilityfor measurements, e.g., PSS/SSS, CRS, CSI-RS as well as CSI-IM which maybe used for interference measurements. Dynamic requests for measurementsand measurement reports may indicate the presence/non-presence ofsignals and/or resources for measurements, e.g., Reference SignalReceived Power (RSRP), Reference Signal Received Quality (RSRQ), CSI,Received Signal Strength Indicator (RSSI), and/or interference (e.g.,using CSI-IM).

Methods and apparatuses are disclosed herein for a dynamic change ofsignal and resource location to reduce interference and enable LAAresource sharing among LAA cells. Methods and apparatuses are disclosedherein for hidden node measurement and reporting. Interferencemeasurements may be triggered and/or reported with a timestamp/timewindow to enable an eNode-B to correlate with the eNode-B's ownmeasurements and detect hidden nodes. During transmission, interferencemeasurements on resources (e.g., CSI-IM) may be dynamically requested(e.g., in a DL grant).

Methods and apparatuses are disclosed herein for CSI reportingoptimization. On demand resource identification and report timing toenable CSI reporting in the active time of the LAA cell. Methods andapparatuses are disclosed herein for new measurement types, which mayinclude but are not limited to the following example types: enhancedRSSI (eRSSI), interference, SINR and/or radar detection. Methods andapparatuses are disclosed herein for opportunistic measurement andreporting. Methods and apparatuses are disclosed herein for a dynamicindication of measurement reporting.

A WTRU may, or may need to, measure a signal or channel or one or morecharacteristics (for example, power, signal-to-interference plus noiseratio (SINR), signal-to-noise ratio (SNR), and the like) of a signal orchannel when the presence or availability of the signal or channel maynot be regular (for example, periodic) or may not be according to aknown or configured schedule. For example in an LTE cell, referencesignals (such as CRSs) may be present in all DL subframes, while in acell which may turn off the transmission of reference signals, such asan LTE-U or LAA cell, such reference signals may (or may only) beavailable sometimes or in some DL subframes and may not be available atother times, for example during off periods, LBT, or transmission gaps.Measurement accuracy and/or system performance may be impacted if a WTRUmay not know when signals which it may or may need to measure may or maynot be present.

In a one example, a WTRU may receive an indication, for example, from aneNode-B or cell, which may inform the WTRU when one or more signalsand/or channels which may be used (for example, by the WTRU) formeasurements may be present or not present (for example, transmitted ornot transmitted by the eNode-B or cell or another eNode-B or cell). Theindication may be provided dynamically, for example, via physical layersignaling such as in a Downlink Control Information (DCI) format. Theindication may include the resources on which the one or more signalsand/or channels may be present or not present which may include timeand/or frequency resources. These resources may be referred to aschannel resources. The indication may include a request to performand/or report at least one measurement, for example using the indicatedone or more signals and/or channels and/or channel resources. Theindication may be referred to as a signal-presence indication ormeasurement-indication and the terms may be used interchangeably. Theindication may or may not include identification (for example, explicitidentification) of one or more signals and/or channels which may be usedfor measurements.

In some examples, the indication may include channel resources which maybe used for measurements and may or may not include informationregarding or identifying the signals and/or channels which may berelated to the measurements. The channel resources may be used (forexample, by the WTRU) for measuring one or more signals and/or channelswhich may be from (or transmitted by) an eNode-B or cell such as aserving eNode-B or cell of the WTRU. The channel resources may be used(for example, by the WTRU) for one or more measurements (for example,for measuring interference) in the absence of some or all signals and/orchannels which may be from (or transmitted by) an eNode-B or cell suchas a serving eNode-B or cell of the WTRU.

In another example, a WTRU may receive an indication, for example, froman eNode-B, which may inform the WTRU on which time and/or frequencyresources (for example, channel resources) the WTRU may perform ameasurement. The indication may be provided dynamically, for example,via physical layer signaling such as in a DCI format. The indication mayinclude a request to perform and/or report at least one measurement, forexample, using the indicated channel resources. The channel resourcesmay be used (for example, by the WTRU) for measuring one or more signalsand/or channels which may be from (or transmitted by) an eNode-B or cellsuch as a serving eNode-B or cell of the WTRU. The channel resources maybe used (for example, by the WTRU) for one or more measurements (forexample, for measuring interference) in the absence of some or allsignals and/or channels which may be from (or transmitted by) an eNode-Bor cell such as a serving eNode-B or cell of the WTRU.

A signal and/or channel which may be used for measurements may be calleda measurement-related signal. A measurement-related signal may be or mayinclude one or more (for example, a combination) of: a synchronizationsignal, a reference signal, PSS, SSS, CRS, CSI-RS, DM-RS (or DMRS),and/or PRS. Channel resources which may be used for measurements may becalled measurement-related channel resources. Measurement-relatedchannel resources may be, or include, channel resources which may carryat least one measurement-related signal. Measurement-related channelresources may be or include channel resources which may be used formeasurements and which may not contain a signal and/or channel (forexample, for or from a certain eNode-B or cell such as a serving eNode-Bor cell of the WTRU). Measurement-related channel resources may be ormay include one or more of CSI-RS and/or CSI-IM channel resources.CSI-RS may be or include zero-power CSI-RS.

For example, a WTRU may perform measurements on zero-power CSI-RS and/orCSI-IM channel resources, for example to measure or determine thepresence of interference.

Measurement-related signals and measurement-related channel resourcesmay be used interchangeably. The WTRU may make a measurement, which maybe in response to a measurement request, using the indicated signaland/or channel, and/or channel resources. The WTRU may report themeasurement in response to a request and/or in response to a measurementtrigger. Dynamic and/or on-demand signal indications, channel resourceindications, and/or measurement requests may enable measurements to bemore optimal for LTE-U.

In an example, an LTE-U cell may wait to use an unlicensed frequencychannel until it may detect the channel as free and/or may have a shorttime during which it may keep (for example, use or continue to use) anunlicensed frequency channel (for example, 4-12 ms). The time duringwhich an LTE-U cell may use (or transmit on) a frequency channel may becalled the active time of the cell. The cell may or may only transmitsignals (which may include measurement-related signals) during itsactive time. Preconfigured measurement periods may not align well withthe active time. The LTE-U cell (or its associated eNode-B) may use (forexample, transmit to a WTRU) one or more measurement indications, whichmay be dynamic or on-demand, to enable and/or request measurements whichmay align (for example, better align) with at least part of the activetime.

In another example, an LTE-U cell (or its associated eNode-B) may changethe resources on which the cell may transmit a channel and/or signal,for example dynamically or from one active time to another active time.The eNode-B or cell may change the resources to adapt its (or thecell's) transmissions to the presence of interference and/or to enablemultiple LTE-U cells to share a frequency channel. The eNode-B or cellmay include channel resources in a measurement indication that mayenable one or more measurements to account for these changes.

In another example, an LTE-U cell (or its associated eNode-B) may changethe resources on which the cell may not transmit (or may transmit withzero power) a channel and/or signal, for example dynamically or from oneactive time to another active time. The eNode-B or cell may change theresources to enable measurements of interference to be, for example,dynamically, targeted in time and/or frequency and/or to enableinterference measurements to be made on some resources while the cellmay transmit on other resources. The eNode-B or cell may include channelresources in a measurement indication that may enable one or moremeasurements to account for these changes.

Not transmit and transmit with zero power may be used interchangeable. Asignal which may be not present or absent may be a signal which may betransmitted at zero power and vice versa.

A channel resource or channel resources may be indicated in time and/orfrequency domains. A time domain indication may include or indicate oneor more of: one or a number of subframes, one or a number of timeslots,one or a number of OFDM symbols, one or a number of time samples, and/orone or a number of frames, among others. The time units (for example,subframes, frames, symbols, and the like) may be LTE time units.

A frequency domain indication may include or indicate one or more of: acarrier frequency (for example, which may be represented by an E-UTRAAbsolute Radio Frequency Channel Number (EARFCN)), a bandwidth, one ormore subcarriers, and/or a set or sets of subcarriers (for example, aset of 12 subcarriers which may correspond to an RB or RB pair), amongothers. A frequency domain indication may (or may be used to) include orindicate one or more RBs (or RB pairs). This may apply when the timedomain (for example, one or more timeslots or subframes) for the one ormore RBs (or RB pairs) may be known or understood (for example, by theWTRU).

A resource element (RE) may correspond to one subcarrier during one OFDMsymbol interval. A RE may be an example of a channel resource which maybe indicated and/or defined and/or identified in both time and frequencydomains. An RB or physical RB (PRB) may indicate and/or define and/oridentify a set of channel resources in both time and frequency domainsor in frequency domain (for example, only).

RB and PRB may be used interchangeably. RB (or PRB) may be used torepresent a certain number of subcarriers such as 12 subcarriers. An RB(or PRB) may correspond to one timeslot. The term RB (or PRB) may beused to represent an RB (or PRB) pair which may correspond to 2timeslots, for example of a subframe. The set of subcarriers which maycorrespond to each RB in an RB pair may be the same, for example, ifthere may be no frequency hopping, or different, for example, if theremay be frequency hopping.

A channel resource may be indicated or identified by one or more of: oneor a number of RBs, a set or sets of RBs, one or a number of REs, and/ora set or sets of REs.

A WTRU may receive a measurement indication and/or an eNode-B maytransmit a measurement indication. The WTRU may receive the measurementindication from the eNode-B. A measurement indication may include anindication of one or more channel resources that may contain or carry ameasurement-related signal. For example, the measurement indication mayinclude or identify a set of PRBs and/or REs which may carry (or notcarry) a measurement-related signal (and/or other signal or signals)such as CRS or CSI-RS, which may be presented in that set of PRBs and/orREs according to rules which may be the rules of licensed LTE. The timelocation, for example, in a subframe, may be known or determined withoutexplicit indication.

In an example, a bit map may be used to indicate the PRB(s). A certainvalue, for example 1, may correspond to signal presence and another forexample, 0, may correspond to absence of the signal. In another example,the indication may include one or more of a starting PRB, a center PRB,a number of PRBs, and/or a bandwidth.

A measurement indication may include an indication of one or morechannel resources which may not contain or carry one or more (forexample, any) measurement-related signals (or one or more or any othersignals) and may be used for interference measurements.

Whether a channel resource may carry a measurement-related signal oranother signal may correspond to whether one or more of the followingmay transmit a measurement-related signal or other signal in the channelresource: the eNode-B or cell which may transmit the measurementindication, a serving eNode-B of the WTRU, a serving cell of the WTRU,an LTE-U cell, and/or an LTE-U cell, for example, of the WTRU and/or aserving eNode-B of the WTRU which may be configured and/or activated.

A measurement indication may correspond to one or moremeasurement-related signals and/or measurement types, for example, CRSmeasurement, CSI-RS measurement, PSS and/or SSS measurement, one or moreof RSRP, RSRQ, RSSI measurement, CSI-IM measurement, and the like. Themeasurement indication may include the signal or signals and/or the typeor types explicitly, for example by a value or values which may beconfigured by the eNode-B to correspond to one or more signals and/ormeasurement types. The signal or signals and/or type or types may beindicated implicitly, for example, by the DCI format of the measurementindication or the RNTI used to scramble the CRC of the DCI format. TheWTRU may receive different measurement indications for differentmeasurement-related signals and/or measurement types.

Based on at least a measurement indication which may indicate thepresence or absence of a measurement-related signal and/or a measurementtype, the WTRU may expect the indicated signal (or the signal or signalsrelated to the measurement type) to be present or absent on the channelresources (for example, in time and/or frequency) indicated. The WTRUmay determine the time and/or frequency resources on which a signal mayor may not be present using (or also using) other information such asconfiguration received from the eNode-B, a priori known time and/orfrequency locations, and the like.

A WTRU may perform a measurement on channel resources which may bedetermined as function of a measurement indication and/or one or moreother indications, definitions, or rules. For example, the WTRU mayperform the measurement on the channel resources which may be determinedfrom a combination of a measurement indication and definitions or rulesof the licensed LTE. In an example, the frequency resources (forexample, RBs) for a signal may be included in the measurement indicationwhile the time resources (for example, symbols in a subframe) may be thesame as defined for LTE. In another example, the time resources (forexample, symbols in a subframe) for a signal may be included in themeasurement indication while the frequency resources (for example, RBs)may be the same as defined for LTE.

The time period for or during which a WTRU may perform a measurement(for example, a certain measurement) may be referred to as a“measurement period” and may be expressed in milliseconds (ms or msec),frames, subframes, timeslots, OFDM symbols, time samples, and the like.“Measurement indication” and “measurement period indication” may be usedinterchangeably.

A measurement indication and/or time domain indication may include anindication of a measurement period and/or an indication of one or moreparameters of a measurement period which may include at least one of astart time, an end time, a length of time, and a pattern of time. Ameasurement indication may include or identify the start of ameasurement period. The measurement indication may include or identifyone or more of the first frame, first subframe, first timeslot, firstOFDM-symbol, and/or first time sample of the measurement period. TheWTRU may receive a measurement period start indication implicitly and/orexplicitly.

In an example, the WTRU may receive a measurement indication in subframen. The measurement indication may be provided and/or received in a DCIsignal or format. The measurement indication and/or receipt of themeasurement indication in subframe n may indicate that the measurementperiod may start in subframe n+x. The value of x may be dynamic, forexample, indicated in the same DCI, and/or configured, for example, bysignaling such as higher layer (for example, RRC) signaling from theeNode-B. The value of x may be a fixed or known value such as 0, 1, 2,3, or 4. For TDD, the value of x may be a function of the TDD UL/DLconfiguration of the LAA cell. The value of x may be 0 which mayindicate the measurement period may start in the same subframes as theone in which the measurement indication may be received. The value of xmay not be included in the DCI.

In another example, the WTRU may use the start of the active time of anLAA cell for the start of the measurement period. The start of theactive time may be indicated explicitly such as by a DCI format from theeNode-B or may be blindly determined by the WTRU, for example, based ondetection of one or more signals such as one or more of PSS, SSS, CRS,busy signal, and the like.

A measurement indication may include or identify the end of ameasurement period. The measurement indication may include or identifythe last subframe and/or timeslot and/or OFDM-symbol and/or time sampleof the measurement period. A WTRU may receive a measurement period endindication implicitly and/or explicitly.

In an example, the WTRU receive a measurement indication in subframe n.The measurement indication may be provided and/or received in a DCIsignal or format. The measurement indication and/or receipt of themeasurement indication in subframe n may indicate that the measurementperiod may end in subframe n+x. The value of x may be a dynamic, forexample, indicated in the same DCI, and/or configured, for example, bysignaling such as higher layer (for example, RRC) signaling from theeNode-B. The value of x may be a fixed or known value such as 0 whichmay indicate the measurement period may end in subframe n+0 (forexample, the subframe in which the measurement indication may bereceived). The value of x may not be included in the DCI.

In another example, the WTRU may use the end of the active time for anLAA cell for the end of the measurement period. The end of the activetime may be indicated by the eNode-B, for example by a DCI format. Theend of the active time may be determined by the WTRU from one or moreindications, for example, which may be provided by the eNode-B, such asthe start of the active time, active time duration, amount of time leftto the end of active time, a time such as the first time the WTRU may bescheduled with resources on the LAA cell. One or more of the indicationsmay be provided and/or received in physical layer signaling such as aDCI format. The end of the active time may be determined by the WTRUbased on the absence of one or more signals or the measurement of one ormore signals below a threshold. The one or more signals may include oneor more of the measurement-related signals such as PSS, SSS, and CRS.

A measurement indication may include or identify the length of themeasurement period. The length may be expressed in one or more of anumber of frames, subframes, timeslots, OFDM symbols, time samples, andthe like. A WTRU may use the indications of a measurement period lengthand a measurement period start to calculate or determine the end of themeasurement period. A WTRU may use the indications of a measurementperiod length and a measurement period end to calculate or determine thestart of the measurement period. For example, a WTRU may receive anindication of a measurement period length of y in subframe n. If thestart of the period may be in subframe n+x, then the WTRU may determinethe end of the period to be in subframe n+x+y.

Following the start of a measurement period and/or during (or during thelength of) a measurement period for a certain measurement, a WTRU maybegin making the measurements or may continue to make the measurements.The WTRU may combine the new measurements of a certain type withprevious (for example, stored) values of the same type, for example theWTRU may use the new measurements in a filtered or averaged version ofthe measurement. The WTRU may make the measurement on the channelresources which may be indicated, for example, by at least a measurementindication.

Upon the end of a measurement period or the end of the duration of ameasurement period for a certain measurement, the WTRU may stop makingthe measurements. For a type of measurement, the WTRU may store a numberof the measurements (for example, measurement samples) and/or arepresentative value (for example, a filtered or averaged value) whichthe WTRU may use, for example when the measurement may be activatedagain at a later time. The WTRU may report a value for or related to themeasurement to the eNode-B.

A measurement indication may include or identify a pattern of time unitsor time periods for the measurement period. The pattern may be referredto as a measurement pattern. The measurement pattern may include oridentify a pattern of subframes and/or timeslots and/or OFDM symbolsand/or time samples which may constitute, comprise, or be included inthe measurement period. A measurement-related signal which may beindicated to be present or measured during a measurement period with atime unit pattern (for example, a subframe pattern), may or may only bepresent (for example, transmitted by the eNode-B) in the time units (forexample, the subframes) which may be indicated by the pattern. Themeasurement related signal may not be present (for example, nottransmitted by the eNode-B) in other time units (for example,subframes).

Absence of one or more signals (for example, all signals) may beindicated by a measurement pattern. The measurement pattern may indicatea time unit pattern during which the one or more (for example, all)signals may not be present (for example, may not be transmitted by theeNode-B).

For a measurement-related signal with a time unit (for example,subframe) pattern, the WTRU may (or may only) consider or use formeasurement purposes channel resources (for example, indicated orconfigured channel resources) which may be located in the time units(for example, subframes) indicated in the time unit (for example,subframe) pattern. For example, the WTRU may receive a bit map, forexample, “0101010101” which may correspond to the subframes in a radioframe. The bit map may indicate in which subframes one or moremeasurement-related signals may be present (or absent), for example,present in the second, forth, sixth, eight and tenth subframes of theradio frame. The WTRU may (or may only) perform measurements on thechannel resources of the one or more measurement-related signals in theindicated subframes (for example, subframes indicated as present orabsent which may depend on the measurement type).

In another example, the pattern may be relative to the start of themeasurement period, for example, every nth subframe beginning withsubframe n+k where n may be the subframe in which the measurementindication or measurement pattern may be received and k may be greaterthan or equal to 0. A measurement pattern may identify specific timeunits (for example, subframes) in which a signal or signals may bepresent or absent. The pattern may determine the measurement period. Forexample the duration of the pattern may be the duration of themeasurement period. A measurement pattern may be (or may be assumed tobe) repeated within the measurement period. The measurement-relatedsignal may be present (or absent) and/or measured (for example, by theWTRU) in time units (for example, subframes) of the pattern which mayfall within the measurement period. The measurement pattern may be (ormay be assumed to be) the same in one or more (for example, all) frameswithin (for example, at least partially within) the measurement period.The measurement-related signal may be present (or absent) and/ormeasured (for example, by the WTRU) in time units (for example,subframes) of the pattern which may fall within the measurement period.

Different LTE-U eNode-Bs and/or cells may have or use differentmeasurement patterns. For example, two or more LTE-U cells may bedeployed on the same frequency channel and/or may be active at the sametime. One or more of their measurement periods may overlap in time. Iftheir measurement patterns do not overlap, each LTE-U cell may transmitits measurement-related signals according to its measurement pattern andmay not interfere with the measurement-related signals of another LTE-Ucell.

A measurement indication may include or identify an indication of one ormore cells (for example, LTE-U cells) and/or one or more frequencychannels (for example, LTE-U frequency channels, which may or may notcorrespond to an active LTE-U cell) for which the measurement indicationmay apply. The measurement indication may include or identify one ormore cell IDs or a range of cell IDs. The measurement indication mayinclude or identify one or more frequency channels (for example, byindex which may correspond to a configured list of LTE-U frequencychannels).

A WTRU may receive a measurement indication for one or more LTE-U cells.The WTRU may receive different measurement indications for differentLTE-U cells.

A measurement indication or another means or indication may (or mayinclude an indication to) activate (or enable or start) and/ordeactivate (or disable or stop) one or more measurement proceduresand/or mechanisms. A measurement indication may include an indication tostart or stop making one or more measurements which may be configured byphysical layer and/or higher layer signaling such as RRC signaling. Anindication of the start of active time for an LAA cell may enablemeasurements related to the LAA cell. An indication of the end of activetime for an LAA cell or the completion of the duration (for example, anindicated duration) of the active time of the cell may disablemeasurements related to the LAA cell and/or enable measurements relatedto one or more other cells and/or users (or potential users) of achannel.

In an example, a WTRU may receive an indication, for example, from theeNode-B, which may activate a set of measurements and/or measurementprocedures and/or mechanisms which may (or may only) apply for an LAAcell or during active time for an LAA cell. Measurement configurationsmay be provided, for example, by the eNode-B, separately and/or with theindication. The indication may be the start of the active time for theLAA cell which may be explicitly indicated (for example, by physicallayer signaling) or blindly detected by the WTRU. The indication may beor may be included in or with a measurement indication.

A WTRU may receive an indication, for example, from the eNode-B, whichmay deactivate a set of measurements and/or measurement proceduresand/or mechanisms which may (or may only) apply for an LAA cell orduring active time for an LAA cell. The indication may be the end of theactive time for the LAA cell or the start of the inactive time for theLAA cell. The indication of the end of active time may be replaced bycompletion of the duration of the active time.

A WTRU may receive an indication, for example, from the eNode-B, whichmay activate a set of measurements and/or measurement procedures and/ormechanisms which may be apply during (or only during) inactive time foran LAA cell, such as those related to measuring other LAA cells and/orWiFi users which may be deployed on the same channel. The indication maybe the end of the active time for the LAA cell or the start of theinactive time for the LAA cell. The indication of the end of active timemay be replaced by completion of the duration of the active time. Theindication may be or may be included in or with a measurementindication.

Following receipt of an indication to activate (or start or enable)certain measurements, the WTRU may begin making the measurements or maycontinue to make the measurements. The WTRU may combine the newmeasurements of a certain type with previous (for example, stored)values of the same type, for example the WTRU may use the newmeasurements in a filtered or averaged version of the measurement. TheWTRU may make the measurement on the channel resources which may beindicated, for example, by at least a measurement indication.

Upon receipt of an indication to deactivate (or stop or disable) certainmeasurements, the WTRU may stop making the measurements. For a type ofmeasurement, the WTRU may store a number of the measurements (forexample, measurement samples) and/or a representative value (forexample, a filtered or averaged value) which the WTRU may use, forexample when the measurement may be activated again at a later time. TheWTRU may report a value for or related to the measurement to theeNode-B.

A measurement indication may be provided in physical layer signalingsuch as in a DCI signal or format. An eNode-B may transmit themeasurement indication and/or a WTRU may receive (for example, from theeNode-B) the indication. A measurement indication and/or the RNTI whichmay be used to scramble the CRC format of the DCI format may be at leastone of cell-specific, WTRU-specific, or specific to a group of WTRUs. Ameasurement indication may be provided to or intended for a group ofWTRUs, for example by using a group RNTI. One or more WTRUs which may beconfigured with that group RNTI may receive the same measurementindication. A measurement indication may be provided via resources (forexample, PDCCH or EPDCCH) on a cell in licensed spectrum such as thePCell or another cell. A measurement indication may be provided viaresources (for example, PDCCH or EPDCCH) on a cell in unlicensedspectrum such as the LAA cell to which the measurement indication mayapply or another cell. A measurement indication may be included insignaling (for example, a DCI format) which may be separate or differentfrom one or more other signaling (for example, DCI formats) such assignaling (for example, DCI formats) which may be defined or availablefor LTE of a certain release such as Release 12. A measurementindication may be included in signaling (for example, a DCI format) forwhich the purpose or intent may or may only be to provide a measurementindication. A measurement indication may be included in signaling (forexample, a DCI format) which may have at least one purpose or intentwhich may be separate or different from a measurement indication. Forexample, a measurement indication may be included with a DL grant, forexample, for resources on an LAA cell or channel.

The eNode-B may transmit and/or the WTRU may receive (for example, fromthe eNode-B) configuration information which may be relates to LAAmeasurements. The configuration information may be provided in higherlayer signaling such as RRC signaling. The configuration information mayinclude parameters and/or sets of parameters which may be referenced byindex or other identity, for example in a measurement indication. Forexample, one or more sets of channel resources may be identified for oneor more measurement-related signals and/or measurement types. Toidentify the channel resources for a measurement-related signal and/ormeasurement type, an index or identity which may correspond to thedesired channel resources may be used in the measurement indication.

In another example, one or more measurement patterns may be identifiedfor one or more measurement-related signals and/or measurement types. Toidentify a measurement pattern for a measurement-related signal and/ormeasurement type, an index or identity which may correspond to thedesired measurement pattern may be used in the measurement indication.

Whether a measurement indication may be cell-specific, WTRU-specific,and/or group-WTRU specific may be specific to or determined by theeNode-B or cell which may provide the indication.

Whether a measurement indication may be cell-specific, WTRU-specific,and/or group-WTRU specific may be specific to or determined by the cellor frequency channel for which the indication may be provided.

A measurement indication which may be cell-specific may have an RNTIassociated with it which may be known and/or used by some (for example,all WTRUs) in the cell. The measurement indication may (or may also) beprovided to a WTRU or group of WTRUs in dedicated or group signaling(for example, using an RNTI such as a C-RNTI which may or may only beknown to the WTRU or a group RNTI which may or may only be known to thegroup of WTRUs).

A measurement indication may be or include a measurement request. Ameasurement request may be or include a measurement indication.Embodiments which may apply to a measurement request may be applied to ameasurement indication and vice versa and still be consistent with thisdisclosure. Measurement request and measurement indication may be usedinterchangeably.

A measurement indication may request one or more measurements beperformed for example on one or more of the resources which may beindicated with the request. A measurement indication may request anon-demand or aperiodic measurement which may be performed, for exampleusing indicated channel resources and/or over at least part of anindicated or otherwise known or determined measurement period.

A measurement request may be explicit (for example, a bit included in ameasurement indication or other signaling or indication). A measurementrequest may be implicit, for example a measurement indication for ameasurement-related signal may imply a request for the relatedmeasurement.

An eNode-B may provide the measurement indication or request to one ormore WTRUs. A WTRU which may receive the indication or request mayperform the measurement, for example using indicated channel resourcesand/or over at least part of an indicated or otherwise known ordetermined measurement period. For example, an eNode-B may provide oruse a measurement indication to a WTRU to indicate that a signal orsignals (for example, CRS) may be present in a measurement period ofsubframes. The eNode-B may indicate the starting subframe or thestarting subframe may be the subframe in which the eNode-B may providethe indication. The eNode-B may indicate a duration of subframes duringwhich the signal or signals may be present. For example, if the eNode-Bmay have taken or may expect to transmit one or more signals or channels(which may include the indicated signal or signals such as CRS) for atleast N (for example, the next N) subframes, the eNode-B may indicate ameasurement period of N subframes.

The eNode-B may request the WTRU to perform and/or the WTRU may performa measurement such as an RSRP measurement during at least part of themeasurement period. The WTRU may combine measurements it may make duringthe measurement period with each other and/or with previous measurementsto determine a filtered, averaged, or otherwise combined measurementwhich the WTRU may report and/or use for reporting decisions.

A measurement request may be for a current LAA cell or channel or adifferent LAA cell or channel. A current LAA cell may be one which maybe configured as a serving cell and/or activated, for example, for theWTRU to which the request may be made. A current LAA channel may be thefrequency channel of a current LAA cell. A measurement request mayinclude one or more indications or parameters of a frequency channel onwhich a WTRU may make one or more measurements such as the requested orenabled measurement. The indications and/or parameters may include oneor more of a carrier or center frequency (for example, which may berepresented by EARFCN), a bandwidth, and/or an identity or index of afrequency channel which may be included in a configuration (for example,a configured list) of frequency channels. The configuration may identifythe carrier frequency and/or bandwidth and/or other parameters of thechannel.

Measurement may be used to represent a single or specific measurementand/or the combination of one or more measurements of the same ordifferent types. The combination may result in a single value which maybe reported. The measurement indication or other request or indicationmay provide resources such as UL resources (for example, on the PCell,the LAA cell for the requested or indicated measurement ormeasurements-related signal or signals, or a another cell) on which theWTRU may report the requested or indicated measurement or other valuewhich may be related to or determined from the requested or indicatedmeasurement or measurement related signal or signals.

The eNode-B may request the WTRU to report the measurement and/or theWTRU may report the measurement using UL resources (for example, PUCCHand/or PUSCH resources) which the eNode-B may provide with themeasurement indication or request. The WTRU may report the measurementwhen UL resources may be provided (for example, at a later time) forthat or another purpose.

UL resources which may be provided and/or used for a measurement reportsuch as an LAA measurement report may be resources (for example, PUCCHand/or PUSCH) on a cell in licensed spectrum such as the PCell oranother cell. UL resources which may be provided and/or used for ameasurement report such as an LAA measurement report may be resources(for example, PUCCH and/or PUSCH) on a cell in unlicensed spectrum suchas the LAA cell to which the measurement indication, request, or reportmay apply or another cell.

The WTRU may report the measurement according to a schedule which may beconfigured and/or based on a triggering event such as the measurementcrossing a threshold or the change of the measurement crossing athreshold.

FIG. 4 is a signaling diagram of an example method for channelmeasurement and reporting mechanisms for Long Term Evolution (LTE)operation in an unlicensed band. The WTRU may take or make one or moremeasurements. Further, the WTRU may report the measurements or mayreport the measurements if they exceed (or satisfy) a threshold, orreport the fact that the measurements exceed (or satisfy) a threshold.The WTRU may receive a dynamic signal and/or interference measurementrequest from an eNode-B and may report the use of an LAA (or unlicensedband) cell back to the eNode-B. In an example shown in signaling diagram400, an eNode-B 401 and a WTRU 402 may share use of an LAA channel withanother user of the LAA channel. The channel may initially be in used420 by the other user and then enter a free period 430. After the freeperiod, the eNode-B 401 and the WTRU 402 may begin to use the channel440. The eNode-B 401 and the WTRU 402 may be part of an LAA cell. In anexample, the LAA cell may indicate the subframe (or window of possiblesubframes) and/or time/frequency resources to be used by the WTRU totake or make the measurements. For example, the eNode-B 401 may send ameasurement request 450 to the WTRU 402 for the WTRU 402 to take or makemeasurements. In an example, the measurement request 450 may be includedin a downlink grant from the eNode-B 401 to the WTRU 402. Themeasurement request may include an indication of the time and/ortime/frequency resources to measure reference signals or interference inthe unlicensed band. The resources may correspond to CSI-RS, zero power(ZPR) CSI-RS, CSI-IM, RE set, subcarrier set and/or others.

In an example, the WTRU 402 may receive data and take a firstmeasurement in a subframe (SF) n 460. The WTRU 402 may also take asecond measurement in SF n+1 and a third measurement in SF n+2. The WTRU402 may then report the measurements 490 back to the eNode-B 401.

In an example, in addition to the measurement, the report 490transmitted by the WTRU 402 may also indicate a time indication and/orthe subframe (or window of subframes) and/or resources associated withthe measurement (for example, when the measurement occurred and/orexceeded the threshold). The time indication may at least one of: a timestamp (absolute or relative to the request), a time window (for example,a start and stop time), or the amount of time (for example, the numberof SFs, time resources or symbols).

In an example, a WTRU may transmit a measurement report, for example toan eNode-B or cell. A measurement report may include one or more of thefollowing: the measurement value or a representative value for themeasurement; an indication of the time (for example, a timestamp or timewindow) and/or the amount of time at or during which a measurement orother value was evaluated; an indication of the time (for example, atimestamp or time window) and/or the amount of time at or during which ameasurement or other value met or exceeded a certain criteria; anindication of the time at which a measurement evaluation started; cellID (for example, of a LAA cell) which may correspond to the measurement;frequency or frequency channel information (for example, carrierfrequency) of the channel to which the measurement may correspond; andchannel resources (in time and/or frequency) on which the measurementmay have been made and/or to which the report may correspond.

An indication of time may be absolute such as an SFN, or relative suchas an offset in time (for example, in subframes) from a start time whichmay be the subframe in which a measurement indication may have beentransmitted or received. An indication of time and/or amount of time maybe a time window such as a measurement period. The time window may havea start time and/or a duration. One or more of the start time and/orduration may be known and may not need to be included in the report. Forexample, the start time may be the subframe n in which the measurementrequest may have been transmitted and/or received or a subframe offset k(for example, k=4) from that subframe n. An indication of time and/oramount of time may be a number of time periods (for example, a number ofsymbols or subframes). An indication of the time and/or the amount oftime at during which a measurement or other value met or exceeded acertain criteria may be a number of time periods or may be a ratio orpercent of time with respect to a time during which a measurement orother value may have been evaluated.

In an example, an evaluation time window may be N time periods (forexample, subframes) and a measurement may have met a criteria (forexample, above or below a threshold) K times (for example, in Ksubframes) in the N time periods. One or more of N, K, and K/N may bereported.

Actual values, quantized values, indices representing the values orquantized values, indices to sets of configurations, or otherrepresentations of the values to be reported may be used and still beconsistent with this disclosure. A measurement or representative valuemay correspond to a maximum value, an averaged value, and/or a filteredvalue (for example, by higher layers).

An indication of time and/or amount of time in the report may assist aneNode-B in determining the presence of hidden nodes. For example, if aWTRU may make and report an interference measurement during a certaintime period (for example, on a certain frequency channel) and theeNode-B may not detect the interference, the eNode-B may use thatinformation to learn of interference seen by the that it does not seewhich may be from a hidden node.

FIG. 5 is a system diagram of an example wireless system including ahidden node. As shown in system 500, the WTRU 502 may be incommunication with Node 510 and lie in the transmission range 515 (e.g.,coverage area) of Node 510. WTRU 502 may receive information (e.g., adesired signal) from that Node 510. The same WTRU 502 may also lie inthe transmission range 525 (e.g., coverage area) of Node 520, and,therefore, the WTRU 502 may receive one or more interfering signals(e.g., interference) from Node 520. However, Node 510 may not detect thepresence of Node 520, since Node 510 may be located outside of thetransmission range 525 (e.g., coverage area) of Node 520. In this case,the WTRU 502 may measure the interference from Node 520, may detect thepresence of Node 520 and may report those measurements to Node 510.Consequently, Node 510 may become aware of the presence of Node 520,e.g., the hidden node (from the perspective of Node 510), and may adjustits own transmission(s) accordingly.

Measurements may assist an eNode-B in selecting an appropriate channeland/or SCell to assign to a WTRU which may enable more effective use ofLAA channels. Such measurements may (or may also) enable an eNode-B toswitch between LAA channels, for example quickly such as per active timeperiod.

A WTRU may observe and/or measure a channel and/or one or moremeasurement-related signals and/or may report one or more reportingparameters and/or measurement types, for example to its serving eNode-Bor cell, for example, its PCell or via its PCell.

Reporting parameter, measurement parameter, and measurement type may beused interchangeably. Report, measurement report, measurement feedbackreport, and feedback report may be used interchangeably.

A WTRU may, for example, dynamically, receive implicitly and/orexplicitly a measurement indication for one or more reportingparameters. The WTRU may receive and/or apply separate or differentmeasurement indications for separate or different reporting parameters.

A WTRU may include, for example, in a measurement report or as part of areporting mechanism one or more reporting parameters and/or measurementtypes and/or an indication of the channel resources for which the (oreach) parameter and/or measurement type may have been calculated.

A WTRU may be configured and/or requested, for example, dynamically, bythe eNode-B to make or take a measurement. The configuration and/orrequest may indicate to the WTRU a set of channel resources (such assubframes and/or PRBs) on which it may perform the measurements. TheWTRU may be configured and/or provided with a set of measurement typesit may perform using the resources. The WTRU may use some or all of theindicated channel resources to perform one or more of the configuredand/or provided measurement types.

In a measurement feedback report, the WTRU may indicate the measurementtype that may be included and/or the set or subset of resources (forexample, subset of the channel resources configured or indicated by theeNode-B) which may have been used for the measurement. The set or subsetof resources may, for example be indicated as an index, for example, tothe eNode-B. As an example, a WTRU may report the subframes or timeperiod for which a reporting parameter, for example, CQI, PMI, RI,CSI-RS related parameters or measurements, for example, RSRP, RSRQ,RSSI, eRSSI, interference, SNR, SINR, and the like, may have beenmeasured and/or calculated. The subframes may be identified by an indexor indices (for example, exact or absolute index or indices of thesubframes).

A WTRU may perform a measurement in or using a channel resource bylooking for or measuring a specific measurement-related signal orcharacteristic of a measurement-related signal. The WTRU may report oneor more of the following, for example, for a measurement-related signal:received signal strength, received interference level, received totalenergy and/or power, received noise power, and the like.

A WTRU may perform a measurement in, using, or on a channel resourceregardless of whether or not that resource may contain a (or thedesired, expected, or intended) measurement signal.

The WTRU may report, for example, for a measurement process, a measuredsignal, and/or a measured channel, one or more of: received signalstrength, interference level, total received energy and/or power, noisepower, and the like.

A WTRU which may be configured with measurements (and/or requested toperform measurements) on one or more LAA channels and/or LAA cells orSCells may report or feedback measurements for one or more (for example,any) of the measurement types and/or parameters described herein. Thereport or feedback may be provided or transmitted by the WTRU on theWTRU's PCell and/or one or more of its SCells and/or LTE-U SCells.Feedback or reporting may be one or more of periodic, on-demand,according to schedule, enabled and/or disabled, activated and/ordeactivated, and/or event triggered.

A WTRU may be configured with reporting occasions. The configuration maybe included with the configuration of the measurement type for which theoccasions may apply. The reporting occasions may be subject to one ormore of activation/deactivation, enable/disable, start/stop, and/or anon-demand request.

A WTRU may be configured with LAA channel measurement gaps. Themeasurement gaps may be configurable, for example, dynamically, whichmay enable WTRU measurements to reflect use of the LAA channels whichmay be non-uniform.

A WTRU may perform measurements on one or more LAA channels and/or LAAcells, for example, aperiodically and/or when triggered by its servingeNode-B or cell (for example, PCell). For example, the WTRU may beconfigured or pre-configured (and/or receive measurement indications)with one or more measurement types and may make measurements of one ormore of those measurement types, for example, autonomously and/or whenrequested. The WTRU may report some or all of the measurements, forexample, upon (or in response to) receiving a request for measurementfeedback from the eNode-B.

The WTRU may be granted UL resources, for example, in a scheduling grantor in a measurement feedback request. The resources may be granted in aDCI format which may be provided via a (E)PDCCH transmission which maybe from a PCell. The WTRU may report measurements which it may take (ormake) on one or more LAA channels and/or LAA cells or SCells on thegranted UL resources.

For example, the WTRU may be configured semi-statically with a pluralityof sets of LAA channels and/or LAA cells for which it may makemeasurements. The sets may or may not include LAA cells and/or channelsactivated for the WTRU. The sets may or may not include LAA cellsconfigured as serving cells for the WTRU. The sets of LAA channelsand/or LAA cells may be configured with specific time and/or frequencyresources on which the measurements may be made. In one example, thetime when a WTRU may make measurements on some LAA channels and/or cells(e.g., one or more channels and/or cells which may not be configuredand/or activated for the WTRU) may be configured as measurement gaps. Inan example, a set of LAA channels and/or cells may be assigned an index.In another example, each set of LAA channels and/or cells may beassigned an index.

A DCI which may be transmitted to a WTRU may provide a measurementindication to the WTRU. The measurement indication may be or include anLAA measurement request and/or a measurement report request. Theindication may be in the form of an information element, which may be anew information element in an example, or a string of bits. Theindication (for example, codepoints of the string of bits) may requestor instruct the WTRU to perform at least one measurement relatedoperation.

For example, the measurement indication may request (or indicate to) theWTRU to at least make a measurement on one or more (or in an example,each) channel and/or cell of a set of LAA channels and/or cells. The setmay be indicated by an index which may be included with the measurementindication.

In another example, the measurement indication may request (or indicateto) the WTRU to at least report a measurement for one or more (or in anexample, each) channel and/or cell of a set of LAA channels and/orcells. The set may be indicated by an index which may be included withthe measurement indication. A request (or indication) for a measurementreport may include or imply for the WTRU to make the related measurementor measurements.

In a further example, the measurement indication may request (orindicate to) the WTRU to at least report a measurement for each channeland/or cell of a set of LAA channels and/or cells for which themeasurement is above or below a threshold. The number of channels and/orcells for which the measurements may be reported, for example, in acertain report, may be limited to M which may be configured by theeNode-B, known, or determined by the WTRU.

In an additional example, the feedback resources (for example, for theWTRU to use for the measurement report) may be included (for example,identified or granted) in the DCI. The resources may be pre-configuredand may be selected or identified in the DCI, for example, by an indexor other identifier included in the DCI. The resources may be timeand/or frequency resources and may be in at least one subframe forperforming the measurement in an unlicensed band.

The WTRU may then perform the measurement according to the request andsend a report to the eNode-B based on the performed measurement. In afurther example, the at least one subframe for performing themeasurement may be the subframe of the request or a window of subframesbeginning with the subframe of the request. In yet another example, themeasurement report may include an identification of a subframe or SystemFrame Number (SFN) associated with the measurement. In still anotherexample, the measurement report may be sent using the licensed and/orunlicensed frequency band.

In yet another example, the measurement indication may request (orindicate to) the WTRU to delete all previously made measurements for aset of LAA channels and/or cells. This may enable control overmeasurement filtering.

In yet a further example, a measurement indication for a set of LAAchannels and/or cells may request or imply for the WTRU to delete allpreviously made measurements for the set of LAA channels and/or cells.For example, any measurement indication for a set of LAA channels and/orcells may request or imply for the WTRU to delete all previously mademeasurements for the set of LAA channels and/or cells. The measurementindication may request (or indicate to) the WTRU to begin event-basedtriggering of measurement reporting for a set of LAA channels and/orcells.

In yet an additional example, the measurement indication may include oridentify time and/or frequency resources (for example, REs and/or PRBs)on or in which to make the measurements. These resources may beconsidered as configured resources for the measurement.

A measurement indication for or corresponding to a set of LAA channelsand/or cells may include an indication of the set. A set may be orinclude a single LAA channel and/or LAA cell. A WTRU may receive ameasurement indication in a DCI transmitted on an LAA channel and/orcell. The measurement indication may (for example, implicitly) request ameasurement or measurement report for that LAA channel and/or cell.

An eNode-B may provide the measurement indication via a serving cell ofthe WTRU such as the PCell, an LAA Scell, or a non-LAA SCell of theWTRU. Upon or in response to receipt of a measurement indication, theWTRU may make, report, and/or delete measurements in accordance with theindication.

Upon (or after or in response to) being configured and/or requested tomake and/or report LAA measurements (for example, via an LAA measurementindication), a WTRU may perform measurements on the appropriate timeand/or frequency resources. For example, a WTRU may measure the totalenergy included in the configured or identified set of REs and mayaverage it out for the entire bandwidth of a symbol. In anothersolution, a WTRU may sum the total energy in the configured oridentified time and/or frequency resources. The WTRU may also beconfigured with filters to better evaluate the interference. Forexample, a WTRU may be configured with filters to average out themeasurement over multiple OFDM symbols, possibly over a specific timeperiod (for example, 3 measurements within 200 ms). The measurements maybe updated as a sliding window whenever a new valid time and/orfrequency resource is used to make a measurement. A WTRU may beconfigured with reporting thresholds, for example, for WTRU event-drivenreporting. Examples of the thresholds triggering measurement feedbackinclude at least one of: a minimum (or maximum) value has been achieved,an offset change in value is observed over adjacent measurementopportunities, an offset difference between two LAA channels and/orcells has been measured (for example, an offset difference between ameasurement cell and a serving cell).

When reporting the measurement, the WTRU may be configured with a tablemapping measurement ranges to report codepoints. The WTRU may beconfigured with multiple tables, or may be dynamically orsemi-statically provided with a subset of the reporting table. This mayenable different measurement reporting granularity.

An eNode-B may, in a request for measurement feedback (for example, arequest for a measurement report), indicate to a WTRU a measurement type(for example, to measure and/or report) and may indicate the relatedmeasurement configuration. For example, a WTRU may receive a measurementor other indication or request, for example, in a DCI, that may includeinformation on the type of measurement to make and/or report and/or theresources on which the measurement may be taken (or made). The WTRU maymeasure and/or report the indicated one or more measurement types to theeNode-B, for example in granted resources which may be provided with thefeedback (for example, report) request or in the future.

Dynamically indicated resources on which a WTRU may take measurementsmay be considered an aperiodic measurement gap within which a WTRU mayperform a plurality of measurements. The eNode-B may configure the WTRUwith a period of time within which it may make measurements. A WTRUwhich may be configured with a set of resources (for example, subframesand/or PRBs) may perform measurements on a subset of the set ofresources. For example, a WTRU may be configured with multiple subframesto make measurements. The WTRU may make a first measurement on a firstsubset of subframes and a second measurement (for example, which may bethe same type as the first measurement) on a second subset of subframes.The WTRU may be configured to report a plurality of measurements where areport may include one or more of the measurements and/or the subset ofresources on which one or more of the measurements was performed. Themeasurement types may include one or more of those described herein.

A WTRU may perform an averaging process in time and/or frequency domainfor a measurement parameter which may be observed on multiple channelresources which may be indicated in or by a measurement indication.

A WTRU may be configured and/or implicitly and/or explicitly receive aparameter which may describe and/or include an averaging window whichmay be in a time and/or frequency domain. The WTRU may (or may only)consider the channel resources in the averaging process which may bewithin the limits of the averaging window.

As an example, a WTRU may calculate the average interference that it mayobserve or measure in a certain number of, for example, 24, REs (forexample, center REs) which may be in specific OFDM symbols, for example,in every odd OFDM symbol (which may be indicated as a part ofmeasurement indication with a OFDM symbol repetitive pattern of “01”).The WTRU may receive a time average window length of a specific numberof, for example, 4, OFDM symbols. The WTRU may (or may only) considerthe indicated OFDM symbols in the indicated time window, for example,when averaging the interference. For example, the WTRU may (or may only)consider 2 odd OFDM symbols when averaging the interference levels ofthe center 24 REs since there are only two odd numbered OFDM symbols ina 4-OFDM-symbol period.

The WTRU may (or may only) use the channel resources for the measurementwhich may be within the averaging window and which may be indicated inthe related measurement indication. An averaging window may be describedfrequency and/or time domain. The averaging window may be defined by itsOFDM symbol length, for example, 4, and number of subcarriers, forexample, 24.

A WTRU may average a measurement parameter over a certain time frame.The WTRU may report the average value to the eNode-B as a part ofmeasurement report.

The WTRU may report a measurement or measurement parameter for one ormore measurement types when triggered, for example by an event which maybe based on the measurement value or a change in the measurement value.

Occasions for event triggered measurement reporting may bepre-configured. For example, a WTRU may be configured with resourceswhich it may use when a measurement report has been triggered. Inanother example, a WTRU may indicate in an UL scheduling request messagethat the purpose of the UL transmission may be for reportingevent-triggered measurements.

The events that may trigger measurement reports may be configured, forexample per measurement and/or per LAA channel. For example, aninterference measurement of a certain level or value on a first LAAchannel may trigger (or be configured to trigger) reporting of themeasurement (or the event), while the same interference measurementlevel or value on a second LAA channel may not trigger (or may not beconfigured to trigger) reporting of the measurement (or the event).

An event of a first measurement which may trigger a report of or for thefirst measurement may (or may also) trigger or lead to a report of orrelated to a second measurement. For example, the interference measuredon a first LAA channel may trigger a report of that measurement (or theevent) and may (or may also) trigger or result in the report of one ormore other interference measurements which may be taken on one or moreother LAA channels which may be configured.

As another example, an interference measurement on an LAA channel maytrigger reporting of that measurement as well as another type ofmeasurement (for example eRSSI) on the same LAA channel. The measurementthat may trigger a report may not be the measurement that may bereported.

In response to an event which may relate to a measurement such as ameasurement type described herein, a WTRU may transmit a report ormeasurement report, for example, to an eNode-B. The event may or may beconsidered to trigger the report.

One or more events may trigger one or more measurements and/or one ormore reports. An event which may trigger a measurement and/or a reportmay be receipt of a measurement indication which may include a grant forUL resources on which to transmit the report. An event which may triggera measurement and/or a report may be receipt of a grant (for example, anaperiodic grant) for UL resources which may be provided by the eNode-Bto report measurements. The UL grant may include an indication ofchannel resources on which the WTRU may perform measurements. The ULgrant may include or indicate the UL resources where or on which theWTRU should report such measurements.

A report may be triggered when a measurement may be (or may become)greater than (or less than) a configurable (or configured) thresholdvalue. A report may be triggered when a measurement in an occasion (orset of occasions) may be (or may become) offset greater than (or offsetless than) a measurement (for example, of the same type) in anotheroccasion (or set of occasions) that may or may not have been previouslyreported. For example, a WTRU may report a measurement type and may (ormay only) report the measurement type again if it may have increased (ordecreased) by a threshold value from the last report.

A report may be triggered when a measurement type may be (or may become)offset greater (or offset less than) a measurement or measurement typethat may be taken on another LAA channel. For example, the WTRU mayreport a measurement on a first LAA channel if the measured value may beoffset greater than that of a second (for example, reported) measurementon a second LAA channel.

A report may be triggered when a measurement may be (or may become)greater than or less than a configurable (or configured) threshold, forexample for a configurable (or configured) number of times (for example,consecutive times) in a configurable (or configured) duration. Forexample, a WTRU may be configured, for example, dynamically, with a setof resources on which it may make a measurement (for example, RSSI oreRSSI) on an LAA channel. If more than a configured number of individualmeasurements (where each may be measured on a subset of resources withinthe set of resources) may exceed a configured threshold, the WTRU mayreport one or more measurement values and/or an indication that thecondition has been met. This may enable the eNode-B to determine one ormore parameters of the traffic in an LAA channel which may benon-uniform.

An event which may trigger a report may be a trigger for RSRP and/orRSRQ. A report which may correspond to a trigger for RSRP and/or RSRQ onan LAA channel may (or may also) include one or more of RSRP, RSRQ, RSSIor eRSSI, interference, SINR, and/or radar detection measurements. Forexample, when a WTRU may be triggered to report RSRP on an LAA SCell, itmay also include the RSSI or eRSSI of the LAA channel on which the LAASCell may operate.

A WTRU may be configured, for example, dynamically, with a set ofresources on which it may perform multiple measurements which may be ofthe same type and/or which may be on subsets (for example, differentsubsets) of the set of resources. One or more (for example, any) of themeasurements may trigger a measurement feedback report.

In a report which may be triggered by one measurement, a WTRU may(and/or may be configured to) report one or more other measurements. Ameasurement event for one measurement may trigger a WTRU to performand/or report another measurement. For example, a WTRU may be configuredwith a set of subframes on which to take interference measurements. TheWTRU may measure interference on a first subframe. Upon (or as a resultof) comparing it to a threshold, the WTRU may be triggered to measureand/or report interference from one or more other subframes in theconfigured set of subframes.

The WTRU may report one or more of the interference measurements to theeNode-B. The WTRU may include subframe information (for example, asubframe index) for each measurement which it may report. The WTRU may(for example, first) request UL resources for transmission of thereport. The WTRU may transmit the report in UL resources which may havebeen granted with the measurement request (for example, dynamicmeasurement request) from the eNode-B.

In an example, a WTRU may monitor the interference level in the currentconfigured LTE-U SCell where the WTRU may be configured with a relatedthreshold monitoring value. When the interference level of that channelmay go above the configured interference threshold, the WTRU may informthe eNode-B of the event. The eNode-B may change some parameters of thatLTE-U SCell, for example, the frequency channel, when it may receive ahigh interference report from one or more of its WTRUs.

In another example, a WTRU may monitor received signal strength in thecurrent configured LTE-U SCell where the WTRU may be configured with athreshold monitoring value. When the received signal strength level ofthe LTE-U SCell may go below the configured signal strength threshold,the WTRU may inform the eNode-B of the event. The eNode-B may changesome parameters of that LTE-U SCell, for example, the frequency channel,when it may receive the low signal strength report from one or more ofits WTRUs.

In another example, the WTRU may, for example, continuously, monitor oneor more (for example, other) LTE-U cells and/or one or more (forexample, other) LTE-U frequency channels. When a measurement parameterof an LTE-U cell and/or frequency channel may go below and/or above acertain threshold, the WTRU may report the event and/or one of morecharacteristics of one or more of those cells and/or channels to itseNode-B.

The eNode-B may use a measurement indication to request or configure oneor more WTRUs to measure one or more LAA frequency channels. A WTRU may,for example, in response to a measurement indication, measure theinterference level and/or total received power and/or otherinterference-related parameters in the channel resources indicated aspart of the measurement indication. The WTRU may report an interferencelevel and/or one or more other indications for one or more frequencychannels to the eNode-B. An example of another indication may be whetherthe interference level may be above or below a threshold. Anotherexample of another indication may be the cell ID of another LAA cellwhich may be using the channel.

The eNode-B may use the reports it may receive from one or more WTRUs tochoose a frequency channel, for example, one with the lowest detectedinterference level and/or total received power or least averageinterference for some or all of its WTRUs. The eNode-B may use thereports it may receive from one or more WTRUs to determine if and/orwhere and/or near which WTRUs there may be hidden nodes. The eNode-B maychange the frequency channel and/or resources it may schedule on an LAAcell for one or more WTRUs, for example, based on the reports it mayreceive.

A WTRU may perform measurements on and/or provide reports for itscurrently configured and/or activated LTE-U cell and/or one or moreother LTE-U cells and/or candidate frequency channels.

In unlicensed spectrum, the users of the band and hence the interferenceenvironment may change frequently. It may be useful for an LAA cell toadapt to these changes, for example to improve performance.

In one example, an LAA cell may, for example, dynamically, change and/orallocate different resources (for example, time and/or frequencyresources) to different channels and/or signals, such as channels and/orsignals which may be used for measurements. Channels and/or signalswhich may be used for measurements may be called measurement-relatedsignals. Time and/or frequency resources may be called channelresources.

For example, an LAA cell may transmit one or more channels and/orsignals (for example, measurement-related signals), for examplesynchronization signals and/or CSI-RS signals, in channel resourceswhich may experience less interference compared to other channelresources.

LAA cells which may use a channel at the same time may put one or moreof their measurement-related signals in different channel resources. AnLAA cell may modify, for example, dynamically, the time, location (forexample, in frequency) and/or density (for example, repetition density)of one or more channels and/or signals (for example, measurement-relatedsignals), for example to optimize the use of channel resources asneeded.

The term time/frequency may be used to represents time and/or frequency.

CSI reporting which may be for an LAA cell may be provided and/or used.The CSI reporting may be aperiodic, on-demand, and/or triggered.Aperiodic, on-demand, and triggered may be used interchangeably.Reference signal, CSI-RS, CRS, DM-RS, DRS, measurement reference signal,reference resource for measurement, CSI-IM, and measurement RS may beused interchangeably.

In an example, the location of a measurement reference signal for a CSImeasurement may be in a certain time/frequency location of a LAA cell.For example, the time, frequency, or time/frequency location of thereference signal may be determined (for example, by the WTRU) as afunction of at least one of: the subframe number where a CSI (forexample, an aperiodic CSI) measurement and/or reporting may betriggered, the channel number in a LAA cell for which a WTRU may (or mayneed to) measure CSI, a transmission mode which may be configured, aperiodic reporting mode, and an (E)PDCCH candidate number from which aWTRU may receive or may have received a CSI (for example, an aperiodicCSI) measurement and/or reporting trigger. The reference signal may beused, for example, by a WTRU, for CSI reporting such as CQI, PMI, and/orRI reporting, for example according to the transmission mode configured.

The reference signal may be a CSI-RS which may be transmitted within asubframe. The CSI-RS may be: non-zero-power CSI-RS on which a WTRU mayestimate the serving cell channels to measure the CSI; zero-powerCSI-RS, where a WTRU may rate-match around the PDSCH for the zero-powerCSI-RS resources, for example, if a PDSCH may be scheduled for the WTRUor an EPDCCH may be monitored by the WTRU; CSI-IM, on which a WTRU maymeasure interference; or one or more combinations of non-zero-powerCSI-RS, zero-power CSI-RS, and CSI-IM.

A WTRU may be requested or indicated by the eNode-B to report a CSI (forexample, an aperiodic CSI) which may be associated with an LAA cell. Inan example, the reporting (for example, aperiodic reporting) may betriggered in subframe n and the measurement reference signal may belocated in subframe n+k. The measurement reference signal location maybe determined as a function of the subframe number which may betriggered for CSI reporting (for example, aperiodic CSI reporting). TheWTRU may report the CSI (for example, aperiodic CSI) in subframe n+k+s,for example in or via the PCell. The CSI (for example, aperiodic CSI)reporting triggering may be based on a DCI which may be transmitted via(E)PDCCH, for example in or by the PCell. k and/or s may be a number(for example, a predefined number) including 0. k and/or s may beconfigured by higher layer signaling, or may be indicated in the DCI,for example with an RNTI such as C-RNTI or CSI-RNTI.

C-RNTI may be used in place of CSI-RNTI and vice versa and still beconsistent with this disclosure.

A DCI with a certain RNTI (for example CSI-RNTI) may be used to triggerthe CSI (for example, aperiodic CSI) reporting for an LAA cell. The RNTImay be a group RNTI. For example, a DCI with CSI-RNTI may be transmittedin a (E)PDCCH search space (for example, common search space) which maybe in a PCell. A WTRU which may be configured with a LAA cell maymonitor a DCI with CSI-RNTI in (E)PDCCH search space (for example,common search space). A WTRU may measure CSI in subframe n+k if the WTRUmay receive a DCI with CSI-RNTI in subframe n. The RNTI (for exampleCSI-RNTI), which may be a group RNTI, may be configured in aWTRU-specific manner, or may be configured, provided, or predefined in acell-specific manner.

The DCI which may be used to trigger the CSI reporting (for example,aperiodic CSI reporting), for example, the DCI with CSI-RNTI may includeone or more of following: a subframe index or a subframe offset toindicate the subframe (or the number of the subframe) which may containthe measurement reference signal in LAA cell; a configuration of themeasurement reference signal (for example CSI-RS but not limited toCSI-RS) which may include at least one of CSI-RS reuse pattern, CSI-RSconfiguration index, number of antenna ports, CSI process number,physical or virtual Cell ID for scrambling; SCell number or index, forexample if multiple SCells may be used; and Uplink resource information,for example, in the PCell, for CSI reporting. The DCI with CSI-RNTI maybe located in (or only in) a subset of subframes.

A DCI, such as one which may have a purpose other than triggering CSIreporting, may or may also be used to trigger CSI (for example,aperiodic CSI) reporting for an LAA cell. For example, a DCI which maybe used to provide a DL grant (for example, for resources on an LAAcell) may (or may also) be used to (or may include a) trigger for CSIreporting which may include measuring and/or reporting interference. Theinterference may be measured on resources such as CSI-IM resources. Theresources may be indicated (for example, explicitly or by reference to aconfiguration) in the DCI or may be configured separately. The DCI maybe or include a DL grant and/or an UL grant for a serving cell of theWTRU which may be a PCell or SCell in licensed or unlicensed band.

In response to receipt of the trigger, the WTRU may make and/or reportthe indicated or requested measurement. The WTRU may make themeasurement on or using the indicated resources which may be CSI-IMresources.

In another example, the location of a measurement reference signal for aCSI measurement may be in a certain time/frequency location of LAA cell.For example, the time, frequency, or time/frequency location of thereference signal may be indicated via the control information which maytrigger a CSI (for example, aperiodic CSI) measurement and/or reporting.A DCI which may (or may be used to) trigger a CSI (for example, anaperiodic CSI) measurement and/reporting, for example, associated withan LAA cell, may contain the measurement reference signal configuration.The configuration may include at least one of following: the subframeindex or a subframe offset which may indicate the subframe (or thenumber of the subframe) which may contain the measurement referencesignal; the measurement reference signal reuse pattern; andconfiguration for one or more zero-power CSI-RS, non-zero-power CSI-RS,and/or CSI-IM.

In another example, a measurement reference signal may be transmitted,for example, aperiodically, based on the time (or timing or timelocation) of one or more LAA resource bursts. An LAA resource burst maybe at least one of time resources (for example subframes) which may beallocated, for example, continuously or regularly, for an LAA cell, timeresources (for example, subframes) within a time window in an LAA cell,and/or time resources (for example, subframes) which may be allocatedfor a WTRU. Time resources which may be allocated may be configured inthe WTRU, for example, by the eNode-B. Configuration may be via thePCell.

A subframe which may contain the measurement reference signal may bedetermined as a function of at least one of SFN number, for example, inthe PCell, a periodicity which may be configured, a subframe offsetwhich may be configured via higher layer signaling, and/or resourceavailability and/or allocation in an LAA cell.

The measurement reference signal may be located in one (or more) of thesubframes in an (for example, each) LAA resource burst. In an example,the first subframe in an (for example, each) LAA resource burst maycontain the measurement reference signal. The n-th subframe in an (forexample, each) LAA resource burst may contain the measurement referencesignal, where n may be predefined, or higher layer configured.

The measurement reference signal may be located in a subset of subframesof an LAA resource burst. For example, an LAA resource burst which maybe located in a specific SFN may contain the measurement referencesignal.

An indication may be provided and/or used for an LAA resource burstwhich may contain a measurement reference signal. The indication may betransmitted in the first time resource (for example the first subframe)of the LAA resource burst. The indication may be transmitted in thecontrol signaling which may be used to carry the scheduling informationof the LAA resource burst.

In another example, a timer may be used to trigger a CSI (for example,aperiodic CSI) measurement and/or reporting. For example, a timer may beset or configured (for example, in a WTRU) by the eNode-B. If and/orwhen and/or following when the timer may expire (for example, reachzero), the WTRU may measure CSI in a subframe, for example the closest(for example, in time) subframe which may contain the measurementreference signal. One more of following may apply: The timer may beWTRU-specific, predetermined, or configured via a higher layersignaling. The timer may be determined, for example, by the WTRU, as afunction of WTRU mobility. The timer may be paused, for example, by theWTRU, when the LAA cell may not be active, for example, in off state.The time may be resumed when the LAA Cell may become active again. Whenthe timer may expire or reach to zero, the reporting (for example,aperiodic reporting) may be triggered, for example, by the WTRU, rightaway. The LAA Cell may not be active at the time that timer may expireor reach zero. When the timer may expire or reach zero and/or when theLAA Cell may not be active, for example, in off state, the reporting(for example, aperiodic reporting) may not be triggered, for example, bythe WTRU. The reporting (for example, aperiodic reporting) may bepending, for example, in the WTRU, until the LAA cell may become activeagain. The timer may be started or restarted, for example, by the WTRU,when (or following when) the WTRU may report the measurement.

In another example, a PUCCH in PCell may be used, for example, by theWTRU, for reporting (for example, aperiodic reporting) of an LAA cell.For example, CSI reporting (for example, aperiodic CSI reporting) may betriggered for an LAA cell in subframe n and the CSI reporting (forexample, aperiodic CSI reporting) for the LAA cell may be transmittedvia PUCCH in the PCell, for example in subframe n+k+s where subframe n+kmay contain the measurement reference signal. One or more of thefollowing may apply: The CSI reporting mode based on PUCCH (for example,PUCCH CQI feedback type) may be used for CSI reporting (for example,aperiodic CSI reporting). For the CSI reporting (for example, aperiodicCSI reporting), a PUCCH based CSI reporting mode (for example, which mayuse PUCCH resources) may be used for LAA cell and/or a PUSCH based CSIreporting (for example, which may use PUSCH resources) may be used forPCell. A subset of PUCCH based CSI reporting modes may (or may only) beused for LAA cell as a CSI reporting (for example, an aperiodic CSIreporting) mode. For example, wideband PMI/CQI/RI reporting mode (forexample Mode 1-0 and Mode 1-1) may (or may only) be used for aperiodicCSI reporting. The PUCCH resource in PCell for reporting (for example,aperiodic reporting) may be configured via higher layer signaling in aWTRU-specific manner.

The PUCCH resource may be indicated in the associated DCI which may beused for reporting (for example, aperiodic reporting) triggering. ThePUCCH resource may be determined as a function of the PUCCH resourceindex in the associated DCI. The starting (E)CCE number of the (E)PDCCHwhich may contain the reporting (for example, aperiodic reporting)triggering may be used to indicate the PUCCH resource index for the CSI(for example, aperiodic CSI) reporting.

One or more (for example, two) types of CSI reporting (for example,aperiodic CSI reporting) modes may be used for LAA cell. For example, aPUCCH based CSI reporting (for example, aperiodic CSI reporting) mode(for example, PUCCH CQI feedback type) and/or a PUSCH based CSIreporting (for example, aperiodic CSI reporting) mode (for example,PUSCH CQI feedback type) may be used.

The CQI feedback type may be determined based on a timer. For example,the PUCCH CQI feedback type may be used if a timer expires, otherwisethe PUSCH CQI feedback type may be used, or vice versa. The CQI feedbacktype may be configured by the eNode-B, for example, via higher layersignaling. If and/or when a CSI reporting (for example, an aperiodic CSIreporting) may be triggered, the CQI feedback type may be based on theconfiguration which may be provided by the higher layer signaling.Alternatively, the CQI feedback type may be dynamically indicated, forexample, in the associated DCI which may be for the CSI report (forexample, aperiodic CSI report) triggering.

One or more (for example, two) RNTIs which may be group RNTIs may bedefined to indicate the CQI feedback type. For example, aCSI-RNTI andpCSI-RNTI may be defined. The aCSI-RNTI may be used to indicate a PUSCHCQI feedback type and the pCSI-RNTI may be used to indicate a PUCCH CQIfeedback type.

Interference measurement reporting which may be aperiodic, on-demand,and/or triggered measurement reporting may be provided and/or used.Aperiodic, on-demand, and triggered may be used interchangeably.Interference measurement, interference level reporting, measuredinterference, interference signal strength, signal power in theinterference measurement reference signal, and measurement in CSI-IM maybe used interchangeably.

In an example, a WTRU may be requested or indicated, for example, by aneNode-B, to measure an interference level in a certain time/frequencyresource (or resources). The time/frequency resource (or resources) forthe interference measurement may be or may include a measurementreference signal which may be located in a subframe. The interferencemeasurement may be performed using the measurement reference signalwithin the subframe. The interference measurement reference signal(IM-RS) may be at least one of CSI-IM, CSI-RS, zero-power CSI-RS, andCRS.

The configuration information for IM-RS may be provided to a WTRU whichmay be requested (or indicated) to measure an interference level usingthe IM-RS. The configuration may be provided by an eNode-B. For example,a DCI may be used to trigger the interference level reporting and theIM-RS configuration may be transmitted in the DCI. The IM-RSconfiguration may include at least one of a reference signal patternand/or reuse pattern; a scrambling code; a power allocation; and asubframe location and/or number.

The DCI may be received in the PCell (or an LAA Cell) and the IM-RS maybe located in the LAA Cell. An interference measurement triggering bitfield may be defined in the DCI which may be an independent bit fieldfrom a CSI (for example, aperiodic CSI) reporting triggering field. ADCI, for example with C-RNTI, may contain the reference signalconfiguration for interference measurement. A DCI which may be used forPDSCH scheduling in the LAA cell may contain the reference signalconfiguration for interference measurement. An RNTI (for exampleinterference measurement RNTI such as IM-RNTI) which may be a group RNTImay be used to trigger the interference measurement for one or more (forexample, a group of) WTRUs.

The IM-RS configuration may be determined as a function of at least oneof the subframe number in which the interference level reporting may betriggered, (E)PDCCH candidate number in which a DCI which may triggerthe interference level reporting may be triggered, and physical orvirtual cell ID for the LAA Cell. The subframe (or subframe number)which may contain IM-RS may be determined as a function of the subframe(or subframe number) in which the interference level reporting may betriggered. A WTRU may monitor one or more (for example, multiple)(E)PDCCH candidates and the IM-RS configuration may be determined as afunction of the (E)PDCCH candidates in which the interference levelreporting may be triggered.

A WTRU may report the measured interference level in a certain subframe,for example, in a PCell. The subframe for the measured interferencelevel reporting may be determined by one or more of following. Thesubframe for the interference level reporting may be determined as afunction of the time location of the subframe containing the associatedIM-RS. For example, if the associated IM-RS may be located in subframen, the measured interference level may be reported by the WTRU insubframe n+k, where n and k may be positive integer numbers.

The subframe for the interference level reporting may be determined as afunction of the time location of the subframe in which the interferencelevel reporting may be triggered. For example, if the interference levelreporting may be triggered in the subframe n, a WTRU may report themeasured interference level in subframe n+k, where n and k may be apositive integer numbers.

Interference, (for example, IM-RS) measurement and/or reporting, forexample, in response to a measurement request, may be conditional on oneor more factors which may be indicated by the eNode-B (e.g., the eNode-Brequesting the measurement and/or report) and/or determined by the WTRU.The one or more factors may include at least whether or not the LAA cellor channel for which the measurement is to be made and/or reported isactive or within an active time, for example, with respect to the WTRU'sserving eNode-B. Active time (for example, start, duration, and/or endof active time) may be indicated by the eNode-B, for example, inaccordance with one or more of the embodiments described herein. Activetime may be determined by the WTRU based on the indication or by blinddecoding for the presence of one or more signals such as a sync or busysignal.

For example, if a WTRU is requested to make an interference measurementin a time resource (for example, one or more subframes, timeslots, orsymbols) of an LAA cell, the WTRU may first determine (for example,prior to the time resource or the start of the time resource) whetherthe LAA cell is in an active time (and/or will be in an active time whenthe measurement is to be made), for example, with respect to the WTRU'sserving eNode-B.

The WTRU may (or may only) make the requested measurement and/or reportthe requested measurement if it determines the LAA cell is (or is not)in an active time and/or will (or will not) be in an active time whenthe measurement is to be made. Active time with respect to an eNode-Bmay mean or correspond to a time when the eNode-B has the LAA channeland/or may transmit on the LAA channel. When the one or more factors onwhich the condition for making the measurement and/or report is or aretrue, the IM-RS resource associated with the measurement and/or reportmay be considered or determined to be valid.

The WTRU may send an interference report if at least one of thefollowing is applicable: the applicable IM-RS resource has beendetermined to be valid, a timer (for example, begun at the time of thelast report) has expired, a reporting trigger has been achieved, and/ora valid reporting resource is available. A reporting resource may beconsidered (or determined to be) valid if at least one of the followinghappens: the WTRU has successfully acquired the unlicensed channel onwhich the measurement report is to be transmitted, the WTRU has beenconfigured with resources on another cell which it may use to transmitthe report, and the reporting resource has not been pre-empted foranother purpose, e.g., transmission of a higher priority UL signal orchannel.

In an example, a separate (for example, different) transmission timeinterval (TTI) length may be used for one cell, for example, the PCell,and another cell which may be an SCell, an LAA cell, and/or an LAASCell. PCell may be used as a non-limiting example for the one or firstcell. Scell may be used as a non-limiting example of the other cell.

For example, a TTI may be defined as 1 ms in PCell while the TTI forSCell may be shorter than 1 ms. One or more of following may apply. TheTTI for SCell may be defined as a number of OFDM symbols which may besmaller than the number of OFDM symbols for a TTI in PCell. In anexample, a TTI in PCell may contain 14 OFDM symbols with normal CP whilea TTI in SCell may contain 2 OFDM symbols with normal CP. A radio frame(for example, for the SCell) may be defined as 1 ms with 7 subframes(for example, with 2 OFDM symbols each). In TDD, a radio frame (forexample, for the SCell) may be defined as 1 ms with 7 subframes (forexample, with 2 OFDM symbols each) which may be used or defined asuplink and/or downlink subframes.

A WTRU may report CSI based on the shorter TTI length and CSI reportingtime (for example, delay) may be reduced.

A wider subcarrier spacing may be used for SCell which may shorten theOFDM symbol length. For example, 15 kHz subcarrier spacing may be usedfor PCell while 150 kHz subcarrier spacing may be used for SCell. TheTTI for PCell may be defined as 1 ms while the TTI for SCell may bedefined as 0.1 ms.

The reference resource which may be used for measurements may use (ormay be assumed to use) shortened TTI. For example, a WTRU may beprovided or indicated in a first reduced TTI occasion (for example in anOFDM symbol n), the reference resource on which measurements may bemade. The location (for example, time location) of the referenceresource may be (or may be a function of) the symbol where theindication may be or may have been received plus k OFDM symbols (where kmay be or may be set to 0).

In an example, the reference resource may be comprised of multiplesymbols which may begin at symbol k. The feedback may be reported inOFDM symbol n+k+s. For example a WTRU may be configured withmeasurements on CRS, and it may be requested or indicated in a firstsymbol of a subframe (such as symbol 0) to perform measurements. Thereference resources for such measurements may be in symbols 4 to 8 (forexample, k=4) and the feedback resources on the PCell may be included inthe second subframe (for example, symbols 14 to 27, or k+s=14).

In another example, the processing time of a CSI measurement may bereduced, for example, if CSI may be outdated. For example, one or more(for example, two) types of CSI reporting may be used. One type of CSIreporting may use a regular CSI measurement which may have k subframeprocessing time. Another type of CSI reporting may use a simplified CSImeasurement which may have s subframe processing time, where k may belarger than s.

One or more of following may apply: Type-A CSI and Type-B CSI. Type-ACSI reporting may have k subframe processing time. If a CSI reporting(for example, an aperiodic CSI reporting) may be triggered in subframen, a WTRU may report a corresponding CSI feedback in subframe n+k. In anexample, k may equal 4 for FDD. A WTRU may (or may need to) perform afull CSI measurement, for example, in this case.

Type-B CSI reporting may have s subframe processing time which may besmaller than k. If a CSI reporting (for example, an aperiodic CSIreporting) may be triggered in subframe n, a WTRU may report acorresponding CSI feedback in subframe n+s. A WTRU may perform a partialCSI measurement, for example, in this case (for example, for Type-B CSIreporting). A subset of CQI may be used. A subset of codebook may beused. A subset of rank may be used. A predefined CQI feedback type maybe used. Alternatively, a WTRU may perform CSI measurement with widebandCQI/PMI/RI, for example, only. In an example, s may equal 1.

Measurement types which may support eNode-B decisions such as LAAchannel section may be provided and/or used. One or more measurementtypes may enable an eNode-B to determine the appropriate LAA channeland/or LAA SCell to use for one or more WTRUs.

An eNode-B may use one or more measurement types described in one ormore embodiments and/or examples herein to determine an (for example,the appropriate) LAA channel and/or LAA SCell to use for one or moreWTRUs.

For one or more (for example, any) of the measurement types describedherein, the trigger (for example, for the WTRU) to begin measuring maybe the configuration (for example, the receipt by the WTRU of theconfiguration) of the measurement by or from the eNode-B. A measurementneed not be monitored continuously when configured by the eNode-B. Ameasurement and/or report may be triggered dynamically, aperiodically,and/or on-demand.

A WTRU may be configured to report an RSSI-like (Received SignalStrength Indicator) measurement. The RSSI-like measurement may be theLTE RSSI measurement. The WTRU may be configured to perform and reportRSSI measurements of one or more LAA channels. The reporting of the RSSImeasurement may be independent of reports for RSRP and/or RSRQ.

The RSSI-like measurement may be an enhanced RSSI (for example eRSSI)measurement and may be comprised of the linear average of the totalreceived power observed, for example in a configurable (or configured)amount of time and/or over a configurable (or configured) bandwidth. Theconfiguration of the eRSSI measurement by the eNode-B may include thebandwidth over which the measurement may be taken (or made) and/or thetime duration for the measurement. In an example, the time duration maybe configured in units of LTE OFDM symbols. In another example, the timeduration of an eRSSI measurement may be sub-LTE OFDM symbol length. Forexample, an eRSSI may be configured over a WIFI OFDM symbol length. TheeRSSI measurement occasion may be synchronized with (for example, withthe timing of) one of the WTRU's serving cells. In another example, theconfiguration of the eRSSI may include a timing offset (for example, inthe order of microseconds) from the timing of one of the WTRU's servingcells.

The WTRU may be configured to make interference measurements on one ormore LAA channels or cells. The WTRU may be provided with resources onwhich it may measure interference. For example, a WTRU may be configuredwith a set of REs and/or subframes on which it may make measurements. Ifthe WTRU may have a serving cell on the LAA channel where it may beconfigured to make interference measurements, the WTRU may assume thatits serving cell may not have transmissions, at least transmissions tothe WTRU, in the resources configured for interference measurements.

A WTRU may measure interference of neighboring LAA cells. The WTRU mayreport interference per neighbor LAA cell or it may report the aggregateinterference measured on multiple (for example, all) neighbor LAA cells.For example, a WTRU may measure interference on neighbor LAAcell-specific resources and may report the sum of multiple (for example,all) neighbor LAA cell interferences. In an example, the WTRU may beconfigured with the resources on which it may measure neighbor LAA cellinterference, for example, by its serving cell (for example, it'sPCell). In another example, the WTRU may autonomously determine theresources on which to measure the neighbor LAA cells' interference. Forexample, a WTRU may determine the neighbor cells' interferencemeasurement resources based on a transmitted signal from the neighborLAA cell. The element from which a WTRU may autonomously determine aneighbor cell's interference measurement resource may include at leastone of: a neighbor Cell ID; busy and/or Synchronization and/or referencesignal configuration; and a preamble.

A parameter of one or more of a Busy and/or Synchronization and/orreference signal configuration may indicate the resources forinterference measurement.

An LAA SCell may transmit a preamble at the beginning of an active timewhich may explicitly or implicitly indicate to the WTRU the interferencemeasurement resource.

A WTRU may measure interference of a neighbor cell on a configurable (orconfigured) signal. For example, a WTRU may measure the interference ofa neighbor cell by a measurement on a reference signal. The WTRU maymeasure the CQI of a neighbor cell and feed that back to its servingcell (for example, PCell) as an interference measurement. The WTRU maybe configured with a precoder assumption to determine the CQI. Inanother example, the WTRU may emulate interference measurements on aneighbor cell signal. For example, the WTRU may be configured with anemulation formula and may obtain the interference measurement byinputting a measurement on a neighbor cell signal and using theconfigured emulation formula.

The WTRU may report enhanced measurement reports when feeding backinterference measurements for one or more LAA channels and/or one ormore neighbor LAA cells. For example, a WTRU may be configured with aset of interference measurement resources on which it may measureinterference (which may be on a channel or from a neighbor cell). Forexample, the set of interference measurement resources may be comprisedof multiple measurement occasions. The WTRU may be configured withand/or use a function to determine the interference and/or what toreport for the interference measurement resource sets.

The function which the WTRU may use and/or the report which the WTRU maytransmit to the eNode-B may include the average interference measurementover the entire set of interference resources. The function which theWTRU may use and/or the report which the WTRU may transmit to theeNode-B may include the maximum or minimum interference measured on anysubset of the set of interference measurement resources. For example,the WTRU may report the interference measurement resource where themaximum (or minimum) interference was measured, possibly along with theinterference value. The function which the WTRU may use and/or thereport which the WTRU may transmit to the eNode-B may include the numberof interference measurement resources that exceeded or fell below aconfigurable threshold value. For example, the WTRU may be configuredwith a set of n interference measurement resources and may report thenumber of measurements k (where k≤n) that exceeded a threshold value.This may enable the eNode-B to determine the typical load of a channelover a period of time.

The WTRU may be configured to measure and/or report the SINR of achannel for an LAA cell. For example, the WTRU may be configured withresources on which it may measure the signal strength in an LAA channel.The WTRU may be configured with another set of resources on which it maymeasure interference plus noise of the LAA channel. The WTRU may reuseone or more of the methods described herein to measure the interferenceplus noise of an LAA channel. The SINR value may be quantized in orderto limit the required feedback. In an example, the SINR may be quantizedto two levels: unusable channel and usable channel. The usability of achannel may be defined as one where the WTRU may receive data from anLAA cell, for example with a certain or configurable (or configured)performance (for example BLER level).

A WTRU may be configured with one or more resources on which it may (ormay attempt to) detect the presence of radar in an LAA channel. Themeasurement (for example, the measurement result or conclusion) may bebinary, for example, either radar detected or not.

The WTRU may be configured with one or more resources (for example,special resources) which may be UL resources (for example, on the PCell)on which it may report radar activity in an LAA channel. Use of theresources to report a radar detection result (for example, radardetected) may be considered high priority and may have precedence overanother (for example, any other) transmission from the WTRU which maycollide with the report (for example, which may be scheduled or intendedfor transmission on the same UL resources).

The radar detection feedback resource may be shared by one or more (forexample, all WTRUs) which may be operating in an LAA channel. The radardetected indication may be such that a (for example, any) WTRU that maydetect radar on the LAA channel may transmit on the resource, forexample, jointly. For example, each WTRU may transmit the same signal.This may ensure the eNode-B may be made aware of the presence of radar.In an example, the WTRU may, for example, periodically or regularly,report the radar detection status of a channel. In another example, theWTRU may trigger and/or transmit a radar detection report upon or as aresult of (for example, only upon or only as a result of) identifyingradar presence in an LAA channel.

In another example, a WTRU may use another (for example, any other)reporting mechanism defined herein to feedback interference-likemeasurements on an LAA channel. The WTRU may use or include anindication which may inform the network that the measurement beingreported may be that of a detected radar, for example, and not a resultof non-radar activity on the LAA channel. For example, a WTRU may beconfigured with interference measurement resources and the WTRU mayreport interference measurements according to an embodiment or exampledescribed herein. Upon or as a result of detecting radar activity on theinterference measurement resource, the WTRU may trigger and/or transmita report to the eNode-B which may include the interference measurement.The WTRU may or may also report or include in the report an indicator(for example, a flag) which may inform the network that the measuredinterference may be from radar and/or that radar may have been detected.The report may include identification of the channel on which the radarmay have been detected.

A measurement may be triggered by the result of another measurement. Forexample, the WTRU may be configured with an interference measurement onan LAA channel. Upon (or as a result of) the interference measurementsatisfying a configured condition (for example, the interference beingpresent on a configured bandwidth) the WTRU may be triggered to performanother measurement type, such as radar detection measurements. This mayenable a reduction in WTRU battery consumption.

FIG. 6 is a signaling diagram of another example method for channelmeasurements and reporting mechanisms for LTE operation in an unlicensedband. A WTRU 601 may receive an indication 603 from an eNode-B 602. Theindication may indicate time and/or frequency resources for performingmeasurements. The WTRU 602 may perform measurements 604 on the indicatedtime and/or frequency resources. The WTRU 602 may report themeasurements 605 to the eNode-B 602.

Although features and elements are described above in particularcombinations, one of ordinary skill in the art will appreciate that eachfeature or element can be used alone or in any combination with theother features and elements. In addition, the methods described hereinmay be implemented in a computer program, software, or firmwareincorporated in a computer-readable medium for execution by a computeror processor. Examples of computer-readable media include electronicsignals (transmitted over wired or wireless connections) andcomputer-readable storage media. Examples of computer-readable storagemedia include, but are not limited to, a read only memory (ROM), arandom access memory (RAM), a register, cache memory, semiconductormemory devices, magnetic media such as internal hard disks and removabledisks, magneto-optical media, and optical media such as CD-ROM disks,and digital versatile disks (DVDs). A processor in association withsoftware may be used to implement a radio frequency transceiver for usein a WTRU, WTRU, terminal, base station, RNC, or any host computer.

What is claimed:
 1. A method performed in a wireless transmit/receiveunit (WTRU), the method comprising: receiving configuration informationindicating a plurality of sets of resource elements (REs), wherein eachof the plurality of sets of REs is associated with aChannel-State-Information Reference Signal (CSI-RS) configuration;receiving a request in Downlink Control Information (DCI), in a firsttime unit, to receive at least one CSI-RS, in at least one set of theplurality of sets of REs, in the first time unit, to perform ameasurement and to report the measurement, wherein the request indicatesthe at least one set of the plurality of sets of REs; receiving the atleast one CSI-RS, in the at least one set of the plurality of sets ofREs, in the first time unit, according to the request; performing themeasurement of the at least one CSI-RS; and transmitting, in at leastone of the first time unit and a second time unit, a measurement reportbased on the performed measurement.
 2. The method of claim 1, whereinthe measurement report includes an identification of the first time unitused to receive the at least one CSI-RS.
 3. The method of claim 1,wherein the measurement report includes an identification of a SystemFrame Number (SFN).
 4. The method of claim 1, wherein the first timeunit is a first subframe and the second time unit is a second subframe.5. The method of claim 4, wherein the first subframe includes a firstplurality of slots and the second subframe includes a second pluralityof slots.
 6. The method of claim 1, wherein the first time unit is afirst slot and the second time unit is a second slot.
 7. The method ofclaim 1, wherein the measurement report is transmitted in the first timeunit.
 8. The method of claim 1, wherein the measurement report istransmitted in the second time unit.
 9. A wireless transmit/receive unit(WTRU) configured to operate on a frequency band, the WTRU comprising: aprocessor; and a transceiver operatively coupled to the processor;wherein: the transceiver is configured to receive configurationinformation indicating a plurality of sets of resource elements (REs),wherein each of the plurality of sets of REs is associated with aChannel-State-Information Reference Signal (CSI-RS) configuration; thetransceiver is configured to receive a request in Downlink ControlInformation (DCI), in a first time unit, to receive at least one CSI-RS,in at least one set of the plurality of sets of REs, in the first timeunit, to perform a measurement and to report the measurement, whereinthe request indicates the at least one set of the plurality of sets ofREs; the transceiver is configured to receive the at least one CSI-RS,in the at least one set of the plurality of sets of REs, in the firsttime unit, according to the request; the transceiver and the processorare configured to perform the measurement of the at least one CSI-RS;and the transceiver and the processor are configured to transmit, in atleast one of the first time unit and a second time unit, a measurementreport based on the performed measurement.
 10. The WTRU of claim 9,wherein the measurement report includes an identification of the firsttime unit used to receive the at least one CSI-RS.
 11. The WTRU of claim9, wherein the measurement report includes an identification of a SystemFrame Number (SFN).
 12. The WTRU of claim 9, wherein the first time unitis a first subframe and the second time unit is a second subframe. 13.The WTRU of claim 12, wherein the first subframe includes a firstplurality of slots and the second subframe includes a second pluralityof slots.
 14. The WTRU of claim 9, wherein the first time unit is afirst slot and the second time unit is a second slot.
 15. The WTRU ofclaim 9, wherein the measurement report is transmitted in the first timeunit.
 16. The WTRU of claim 9, wherein the measurement report istransmitted in the second time unit.
 17. A base station comprising: aprocessor; and a transceiver operatively coupled to the processor;wherein: the processor and the transceiver are configured to transmit,to a wireless transmit/receive unit (WTRU), configuration informationindicating a plurality of sets of resource elements (REs), wherein eachof the plurality of sets of REs is associated with aChannel-State-Information Reference Signal (CSI-RS) configuration; theprocessor is configured to select at least one set of the plurality ofsets of REs; the processor and the transceiver are configured totransmit, to the WTRU, a request in Downlink Control Information (DCI),in a first time unit, to receive at least one CSI-RS, in the selected atleast one set of the plurality of sets of REs, in the first time unit,to perform a measurement and to report the measurement, wherein therequest indicates the at least one set of the plurality of sets of REs;the processor and the transceiver are configured to transmit, to theWTRU, the at least one CSI-RS, in the selected at least one set of theplurality of sets of REs, in the first time unit, according to therequest; and the transceiver configured to receive, from the WTRU, in atleast one of the first time unit and a second time unit, a measurementreport responsive to the request.
 18. The base station of claim 17wherein the first time unit is a first subframe and the second time unitis a second subframe.
 19. The base station of claim 16, wherein thefirst subframe includes a first plurality of slots and the secondsubframe includes a second plurality of slots.
 20. The base station ofclaim 17, wherein the first time unit is a first slot and the secondtime unit is a second slot.